| Author | Message | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
First let's assume that the cost is not going to be a factor. (I have full access to a large sheet metal fab shop and their volume discounts.) What are the drawbacks of using stainless vs. plastic? If stainless is to be used for waste tanks, what type of stainless would be best? Also would surface finish matter (mill run vs. polished), and will the welds need any special treatment like passivating? Thanks | ||
| FAST FRED Rating: N/A |
"What are the drawbacks of using stainless vs. plastic? " After a while the SS will crack/leak at the welds. How long "a while" is ,( may be 5 years , may be 20 ) is the only question. FAST FRED | ||
| Henry R. Bergman, Jr. (Henryofcj)
Rating: N/A |
Yeah...have to agree here with FF. Over time, road vibrations may fatigue the SS welds. I heard SS 308 was a good SS, but no experience here. Do know IT IS $$$EXPENSIVE$$$. Spun manufactured plastic tanks using food quality/rated fresh resins last a very long long time, even in high vibration/bumpy enviroments like coaches. Sometimes plastic is better. And...never start a paragraph with a conjunction. No..wait...what I meant is that with translucent plastic, one can always do a look/see to see and look how full the tanks are with it if the gage breaks. Good luck. | ||
| TWO DOGS Rating: N/A |
I've been thinking about a 1/4 inch thick blackwater tank made out of regular steel...might rust in 20 years...but...I won't be here then... | ||
| Chuck PD4104 Rating: N/A |
1/4" steel would be kinda heavy, don'cha think? Cheap, but heavy. -Chuck PD4104 | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
If I can find a source for SS again (I shoulda stocked up when I had the chance) I will do it myself. I have built tanks with SS, to my knowledge they are still in service. I have seen other's work crack, but speaking from my own experience only, every crack was from what I would call improper attachment methods. If I do it myself, there will be no attachment points on the tank itself. I will build a angle-iron perimeter that supports the tank. I have never seen a SS tank crack when installed this way. Not saying it's not possible, just speakiing from my experience. We used 308 and 316, one was more ductile, the other more for foodservice. Can't rememeber which was which. TD, a 1/4" tank will be one heavy SOB, but if you make it out of 11 ga and coat it, it will last a very long time. This would also hold true for recycled Diesel tanks used for holding tanks. Gary | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Chuck-- You buy any 1/4" plate lately? maybe not so cheap either. Gary | ||
| Marc Bourget Rating: N/A |
Echoing GHG's comment, improper attachment methods would include poor welding technique, including failure to back purge sufficient to avoid chromium precipitation. For full spectrum exposure, go to www.gumpydog.com and check out his two articles on building his own plastic tanks. I can weld stainless. I can weld it properly, but I think my tanks will be plastic. | ||
| Adame Rating: N/A |
My original black water tank was made of 3/16 hot rolled steel. It was installed in 1967. When I bought the bus in '96 it was starting to leak. I replaced it and the gray and fresh tanks with 18 gage 303 or 304 stainless sheet. Can't remember for sure which but it was the common stuff. I made the tanks similar to the fuel tanks, with end pans fitted into an outer wrap. The end pans were spotwelded into whe wrap to fixture them in place. Then it was all seam welded around the edges. Makes a really strong joint. I reasoned that the fuel tanks have lasted 50 years made of steel, the ss should outlast me. One thing I won't do is to pour salt into the waste tanks to prevent freezing. I think that would be bad. | ||
| TWO DOGS Rating: N/A |
I figure a 2 1/2'x2 1/2' cube would weigh 100 pounds...no big deal | ||
| Adame Rating: N/A |
Two Dogs, your tank made from 1/4" X 30" X 30" steel plate would weigh 382.86 lbs. | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Each plate will weigh about 64 lbs. it takes six to make a box That's about 383 lbs empty. Gary | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
So I rounded up to account for the welds  Gary | ||
| TWO DOGS Rating: N/A |
still no big deal...I ain't haulin' 10,000 pounds of passengers | ||
| Marc Bourget Rating: N/A |
Supplemental, From notes jotted during a lecture. 302, 304 and 316 would all be suitable for tank building. 308 is colloquially "an old welder's term" for the 18/8 (%Ni/Chr) rod used to weld any of the three. 302 is very ductile, 304 pretty ductile, 316 is very expensive, but the most corrosion resistant. Onward and Upward | ||
| TWO DOGS Rating: N/A |
how come we keep goin' back to talkin' about ducks | ||
| Adame Rating: N/A |
Just a thought, what are the holding tanks made of in those buses which were originally equipped with them from the factory? I've heard stories about how much work is involved to remove the original stainless bath room, but don't recall any mention of the holding tank. | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Now that I think of it, we used 308 to build cooking grilles, and if you look around it's sold as wire and small bar stock up to 0.7 in. I don't see it sold in any other form. that means we used 316 on the tanks we did and if I recall, it was in replacement of some tanks that were used in farming, where contact with fertilizer was an issue and money was no object. I do have somewhere a 3/8 pipe coupling that has 308 stainless etched right on it. Gary | ||
| TWO DOGS Rating: N/A |
Adame.... My Trailways bus.....had kind of a latrine ... everybody messed in a box....it got douched out when it went to service dept. | ||
| Adame Rating: N/A |
Two Dogs, What was the box made of? I've got to ask, Is Two Dogs your first and middle name? And, if they are, were you named after something you saw two dogs doing when you took your first step? With all due resrect. | ||
| John Rigbyj
Rating: N/A |
Stainless steel is prone to stress corrosion cracking. Better go with plastic. John | ||
| TWO DOGS Rating: N/A |
galvinized sheet metal .............and.... kinda | ||
| MCI Larry (Eurof3)
Rating: N/A |
My buddy had his tanks custom made at a Fiberglass shop. Nice fit and easy removable access panels and seem to be strong as heck. I really liked his idea,until he mentioned the price. I forgot how much now,but it was more than I wanted to spend for 2 tanks. Just another option over SS or plastic. Good luck ! Larry, Naturopath 96A3 85/04 | ||
| Marc Bourget Rating: N/A |
The first MAK convention revealed only one displayed coach with SS tanks. Since I could weld stainless, I resolved then to equip mine with SS. However, the logic of Gumpydog's approach, to me, is compelling. The space up against the bay ceilings, more or less behind the doors frequently is poorly utilized. Custom fabrication of static volume fillers in less utilized areas opens up other space with easier access and better functionality. The complications inherent in back purging SS (the only reasonable way to insure top SS performance) makes the stress relieved PolyPro pretty attractive. YMMV | ||
| James Stacy (Jimstacy)
Rating: N/A |
No one mentioned gages. Moderately priced inductive sensors can be mounted on the outside of a plastic tank and work great virtually forever. Metal tanks require a sonic sender or an exposed plastic tube, both have their problems. Good quality rotational molded tanks are hard to beat no matter what price the steel ones are. IMHO Jim Stacy | ||
| Stephen Fessenden (Sffess)
Rating: N/A |
The plastic tanks in my coach are 22 1/2 years old and they do not leak. Keep that in mind when trying to improve on plastic tankes. Steve Fessenden | ||
| Lin Rating: N/A |
When I first started looking into a bus conversion I read a book by a guy named Willie Lowman that described a method of making fiberglass lined, plywood tanks. The bus I bought was a conversion in progress that had just such a tank. It's only about 60 gallons but it is probably about 15+ years old and still seems to be in fine shape (knock on wood). | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
We all like what we know, right? I'm a steel guy, so I tend to lean toward a metal tank. Since I have a small coach, I need to use every possible square inch. I have looked at premade tanks, unfortunately haven't found any in the dimensions I want. I'm not real comfortable with making my own "Welded-Plastic" tanks. I may to Fiberglass plywood box tanks myself, I'm very familar with that kind of construction, being a boat guy as well. I wish those blue plastic barrels would work, but they waste too much space for me. gary | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
Hi all and thanks for the info. My field experience with plastic tanks has not been good. and like Gary said 'We all like what we know'. Why would the SS tanks be more prone to cracking at the welds than a plastic tank? You have to properly design and support any tank alowing for its size and weight. Adame seems to have a good method for making the tank. As far as tank level goes, I'll run out of fresh before the waste is full (wife and kids would not watch the tank gauge). | ||
| John that newguy Rating: N/A |
Kyle- If you do a search for "stainless steel" or "holding tank", or "waste tank", you should find a thread that includes some URLs to web sites that discuss in great depth, the toxins in sewage and how they manage to erode welds in stainless steel. The URLs (if I remember right), lead to web sites that are marine oriented. The boat guys are usually more concerned with the details, than most RVrs. Rightfully so, I suppose, since it's hard to find parts 40 miles off coast. You didn't mention how much camping you've done in an RV, but I would not suggest assuming that you can (or should) gauge your sewage by the amount of water left in the fresh tank. We stay at service plazas, Walmart, State and Government campgrounds and many odd campgrounds that have had no sewage disposal at the site. During a trip, we will load fresh water whenever we can, to have when there is no water available. But we don't empty the waste at every chance. Doing so would cause more problems, since a waste tank is better emptied when it's got sufficient liquid in it, to flush itself properly. At many campgrounds, you are supplied water and electricity, but must drive to the sewage disposal area to empty a tank. What way do you have to gauge the city water used, that's filling those waste tanks? On a trip, my wife does not rely on confidence that -I- will remember to check everything. I do not expect her to remember all the details either. As long as someone glances at that gauge once a day, it will lessen the chances that they will be glancing at raw sewage trickling down the isle when you apply the brakes. If you don't think that provides incentive.... you ain't lived. | ||
| steve souza (Stevebnut)
Rating: N/A |
I bought aluminum fuel tank for a boat in a scrap yard for $40. 120 gallons. It looked like someone made a mistake at the tank factory cause the writing on it said 3/4" too high. Brand new. I don't think it will last too long though. Steve | ||
| Jim-Bob (Pd41044039)
Rating: N/A |
I used to fill water constantly but I stopped after running the holding tank over once or twice. (overflows to the ground, not in the coach) Our fresh water is 100 gallons, the combined black & grey is 110. No gauges. I only fill the water when the waste tank is dumped and I have never overflowed the waste tank since. I don't worry about running out of water because when I do I don't need any more water 'till I can dump the waste. If we're at a campground I do not fill the water tank unless I am headed for the dump station. I never hook up the water & use the campground's pressure like most campers do. Jim-Bob | ||
| Marc Bourget Rating: N/A |
SS vs. Plastic - an overview IIRC, the observations about SS tank failures involve cracking/corrosion at the weld points, which is especially prevalent in the thin guages used for this fabrication. Welding SS is technical because of a property of the alloy. SS gets its corrosion proof property from a crystaline structure between the iron, nickle and Chromium, with the Chromium being given the major contribution to the corrosion properties, but it requires the compliment of another metal in the SS "partnership", like nickle to make the alloy "work". If Oxygen is present, it, being more chemicically "competitive", bonds more readily to the Chromium forming Chromium Di-oxide, which is distinctive for its blue color. The formation of Cr02 denies the steel its corrosion resistance. Welding temps are sufficient to break down the crystal structure in SS, putting the Chromium into solution. The 18/8 rod will supply more than enough Chromium to restore the corrosion proof properties, IF OXYGEN CAN BE KEPT AWAY. Technicians, building SS tanks for Conversions, do not leave sufficient access panels (if any) to get inside the tanks. This makes it difficult to "back purge" the weld on the thin guages used. The TIG torch may provide sufficient inert atmosphere at the arc, on the outside of the tank, to prevent Cr precipitation, but the inside will be heated to the point that the Chromium is in solution and precipitation will result - exactly where the welded metal is exposed to the "nasty stuff", but "out of view" unless diligent effort is expended. There's various means for back purging, including full immersion in an inert atmosphere, flooding the tank, sealant tape with inert gas supply, etc. The unethical or lazy welder, seeing a nice appearing bead on the outside will go ahead, confident that the uninitiated consumer will overlook his failure to take expensive and/or labor intensive steps to insure a good weld ON THE INSIDE. The high acid content of tomato production plants would make shorter work of SS welds than human waste, if ANY welding of SS made it susceptible to corrosion-related failure. These guys use welding in the construction of SS pressure vessels which, by law, are inspected by ASME certified inspectors. The "corrosion" fault seen with SS construction lies with poor technique, or poor tank design, unrelated to the use of SS, not an inherent property of the SS itself. I have the expensive (level of) equipment to do both. On balance,IMHO, the performance of plastic appears to outweigh the extra work associated with SS fabrication. YMMV Onward and Upward. Marc Bourget | ||
| Pat Bartlett (Muddog16)
Rating: N/A |
I worked in a chemical plant for 22 years, we welded stainless everyday, 304, 316, 321, if properly welded i can't remember a failure that was from welds, now operator error was another issue, some tend to beat on things to remedy their problems and that tends to cause failures. | ||
| Jim Stewart (H3jim)
Rating: N/A |
When I bought my plastic tanks from Ronco (the company that makes them for Ademco and others), the owners son (in his late 40's) said he has never seen one of their plastic tanks fail. these are the roto molded type. | ||
| John that newguy Rating: N/A |
Yup! All of the information regarding sewage and welds in Stainless Steel that I've read, does not mention the type or manner of weld, much less the lack of experience of the welder. They are a bit more general and limit their concern of having found deteriorated welded seams in stainless steel tanks used to contain sewage (Some tanks lasting only a year). Not knowing how the tank was assembled, one would certainly not know how much trust to put into the longevity of the tank's welded seams. Having a fresh water leak and having mom's lunch and dinner by-product all over your Craftsman tools, are two very different problems. Plastic can break at it's seams also, but the saving grace is deterioration can be noted easily by looking at the exterior. The stainless steel seams deteriorate inside the tank, where the deterioration cannot be noted until the crap hits the fan. And of course, another reason you should not have a fan next to your waste tank. | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
I'm with you Pat, the only place I hear about tanks cracking out and dissolving welds is on this board. Having lived in the largest boatyard on the west coast for a few years, I've seen many derelict boats scrapped out, of the ones that had stainless tanks, the tanks were still servicable. Whatever. Gary | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
I have been to Gumpy's site and am duly impressed with his plastic tanks. He has done a great job explaining his methods and materials. I know plastic can work. The usual response to SS is cost and I want to get to the details past cost. My experience camping is enough that I do not trust the water from unknown sources, but that is my personal preference and part of why I'm converting a bus. I like the idea of being totally self contained. My line of work is in custom machinery fabrication. This is why I want to know the pros & cons of different materials used. I also like the idea of keeping the end result simple. Thanks for all your help! | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
After it's all said and done, Who Knows? I may pay Marc to build me a set of tanks. I'm not sure yet. (But I need to decide by Spring) I used to be able to get my hands on surplus SS for free, not so anymore. Functionally speaking, if cost and fabricaion are not issues, I would say there are no drawbacks to SS. Gary | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
I spent lunch web surfing on this subject. All I could find (I must not be any good at surfing), were a few places that used 304L in their holding tanks for lavatory service. 304L SS is an easier grade to bend and the cheaper of common SS alloys (also has superior welding properties. 316 SS is generally more corrosion resistant (esp in salt water) but has problems with chlorine corrosion. The quest for answers continues.... | ||
| Lin Rating: N/A |
I would guess that the millions of RV's on the road have plastic tanks. As some of you, I had an old one. I don't think I ever heard about tank failure being a problem. However if one must have SS and, from the above posts, the main problem seems to be the welds, how about building the container of the tank first, coating or treating the inside and joints, and then putting the lid on? That's the way wood/fiberglass tanks are made. | ||
| Marc Bourget Rating: N/A |
Lin, You can weld yourself into a (tank) corner just as much as you can paint yourself into a house corner. I guess you could add a 1/2" flange, machine for an O-ring and bolt the top on! All things considered, tanks can be rotational molded with cross-linked HDPE, which, hands down, would be the construction material of choice. Polyethelyene is one of the few things truly slicker than S***! Cross linked would be very strong. The only problem is the molds. I once reached an agreement with a molder, provided I build the molds. It would have been for a generic style usable in any bus, but this would have reduced space efficiency and it wasn't worth the effort, just to create a revenue source. Never followed thru. . . Could be a viable project for the MCI-7,8,9 series since sufficient numbers exist to make it work. There'd have to be a concensus on size/placement, also. But I'd be willing to coordinate such a project if sufficient interest were expressed. Can't say it'd be much cheaper $ for $ but it certainly would be better performance. Onward and Upward Marc Bourget | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Actually the biggest problem is the "Fear" of the welds failing. I'm not sure if anyone here has ever SEEN one fail in these conditions. Gary | ||
| Adame Rating: N/A |
Here's a site which explains the issues regarding ss corrosion problems. It does not discuss much the frequency of these failures though: www.azom.com/details.asp?articleid=1177#passivation_and_pickling The article does raise come concerns about the way I made my tanks. While the spot and seam welded pan method makes a mechanicly strong tank by placing the welds in shear instead of tension or "peel", it does cause there to be crevices. There is also the tensile stress caused by shrinkage of the metal surrounding the weld. The article says that failures can occur in crecices or in members subjected to tensile loads when in the presence of chlorides and at temperatures above 140*F. I don't plan to haul salt water and I can't imagine a situation where the welded areas would see 140*F for long. However, I think I will passivate the tanks and probably also coat the inner seams of the waste tanks with a one part urethane just to be safe. This is easy enough to do at this point. | ||
| Russell Barnes (Neoruss)
Rating: N/A |
Those in the over-the-road and rail Tanker industry using SS tanks that haul thousands of gallons of products containing chlorides, iodides, or bromides and they passivate (acids) which smooths the surface and removes the contaminates and iron that starts the corrosion from the bad stuff. And their findings are that the area next to the weld in the heat effected zones is where the problem starts. (much like Mark said) They avoid the weld issues by using "L" (leaded) grade stainless steel and welding wire, and titanium stabilized material. Now the tanker industry has another benefit, they load, haul, dump and then CLEAN. We don't do the last step like they do. They also use inert linings for really nasty stuff so your urethane makes good sense. | ||
| H3 (Ace)
Rating: N/A |
I guess someone needs to address this SS tank issue with Prevost then because my H3 had, and still has but not functional, a SS waste tank! Only reason it's not being used is because now it's mine! When I picked it up at seller's they drained the black tank so that tells me it never failed. It's a 1992! Yea I know! They drain them often and I'll do the same with mine! Ace | ||
| John that newguy Rating: N/A |
Fo' wazis wert: (From here: http://www.mcnallyinstitute.com/04-html/4-1.html) ---------------------- MICRO ORGANISMS These organisms are commonly used in sewage treatment, oil spills and other cleaning processes. Although there are many different uses for these "bugs", one common one is for them to eat the carbon you find in waste and other hydrocarbons, and convert it to carbon dioxide. The "bugs" fall into three categories: - Aerobic, the kind that need oxygen. - Anaerobic, the kind that do not need oxygen. - Facultative, the type that goes both ways. If the protective oxide layer is removed from stainless steel because of rubbing or damage, the "bugs" can penetrate through the damaged area and attack the carbon in the metal. Once in, the attack can continue on in a manner similar to that which happens when rust starts to spread under the paint on an automobile. ---------------------- (Here, I thought a micro organism was always accompanied by a little "Ooooh"...) I have never heard of an RV tank of any type falling apart at it's seams. Usually the connections will fail, the area around the connections or mountings fail, or the vehicle sold before anything is noticed. It's fun to argue about this stuff, but in reality, what's the difference? By the time the thing rots through, it'd have already fallen off the bay ceiling.... (hey Ace...... HAR HAR! just kiddin', man.) | ||
| H3 (Ace)
Rating: N/A |
Yea that's too funny! I can't wait for that to happen! I may wait to let er rip when I go to Ca. so I can spread more "stuff" around! har har har Ace | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Re-Read the text John. "These organisms are commonly USED in sewage treatment, oil spills and other cleaning processes." The text is not talking about a naturally occurring species at least in an RV. Unless you're a Sewage Treatment Engineer, or a Oil-spill cleanup guy, you're not likely to encounter this micro-organizim, and if you ever did, you would probably avoid pouring any in your holding tanks. Gary | ||
| RJ Long (Rjlong)
Rating: N/A |
Kyle - George Lowry built his fresh and grey/black tanks out of plastic, customizing them to fit the space available in his 4106. They're now over 10 years old, and no problems. I've seen them, really slick installation, and inexpensive, too. You can read about their construction here: http://users.cwnet.com/~thall/george.htm HTH, RJ PD4106-2784 Fresno CA | ||
| John that newguy Rating: N/A |
Hey Gary- That stuff -is- used by us RVrs. We buy the crud and toss it in the waste tank for both freshness, and for helping to dissolve the .... err... you know... stuff. Jeez man, you don't have to be a craptologist to use it! | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Before I started turning a wrench, my dad and I ran a small resort that was completely self contained, including a sewage treatment plant. My dad was state certified as a sewage plant operator, he used...believe it or not....Dog food. Ok once and for all, has anyone ever seen a tank crack out, or welds dissolve? Anyone? Show of hands? Anyone....? Gary | ||
| Stan Rating: N/A |
I have repaired cracked welds on two SS tanks used in bus conversions. Both were fresh water and not sewage. | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Improper mounting or welding techniques Stan? Gary | ||
| Pat Bartlett (Muddog16)
Rating: N/A |
After saying what i did about stainless tanks, i still like the idea of a quick look at the plastic tanks when checking the level, you can't do that with stainless, and the lord knows i love stainless....... | ||
| H3 (Ace)
Rating: N/A |
Why not have both? I have plastic for Fresh water! I can see my water level thru the box that they are in. Where's the law that say's you can't mix them or is that in one of those big books I don't have and glad I don't? Ace | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
It appears that FF cut to the heart of the issue rather quickly. It seems that 304L will be suffcient if the corrosion issues are minimized with an appropriate epoxy coating inside covering the seams. This will extend the usefull life of the tank. If/ when I proceed with SS tanks, it will be to custom fit them to minimize wasted space. I will have an access port on the side of the tank covered with a piece of translucent material (maybe I'll use glass)for inspecting the 'quality' of the tank contents. Thanks to everyone who helped me to better understand the issue. Kyle | ||
| Marc Bourget Rating: N/A |
Kyle, I have some 1/4" SS around I got from Bellato Engineering. If you wish, I'll make a bulkhead ring with an O-ring groove for you, just fwd dimensions, including hole pattern. Marc | ||
| Stan Rating: N/A |
Gary: I can't comment on why the tank welds cracked. I am not a certified welder and ran a bead for a friend. I would guess that the tanks were only about 18 or 20 guage and sitting on plywood without any side support. They cracked on the bottom end corners.When I welded the first one I found that I had to start beyond the crack and weld to the center or else the crack would run. You could actually see it run ahead of the puddle. I am not as gited as some on this board who are experts in everything. I just know enough about welding to get myself in trouble. However, I have done quite a bit of machining so I know quite a bit about metals. | ||
| Tony H. (Bluegrass)
Rating: N/A |
Mark I dont know how your S!!! reacts to the Aluminum you are talking about but I have had Aluminum In my 7 for 18 years now and never a leak, I use the Coach 15 to 20 times per year and dump my tanks after every outing. Tony | ||
| Marc Bourget Rating: N/A |
Tony, I don't know how "my" aluminum reacts in "my" waste tank because I wouldn't use aluminum for that purpose. I think the posts above in this thread clearly establish that I would consider either SS or specific forms of plastic. Without specifying any particular useful life, I feel it's safe to say that either of my choices will last longer than aluminum. Simply consider the effect of urine on panel dividers in public restrooms. I see SS and Polyethelyene touted as wide spectrum, severe use, corrosion resistant materials. Aluminum basically is touted as superior only to carbon steel. What it really comes down to is - I'm going to invest pretty much the same amount of work in building a custom tank set regardless of whether they're made of SS, plastic or Aluminum, with the SS being the most expensive material cost, plastic the least (I think). "What's in your wallet?, er Conversion!" Please don't take this as a personal comment, I put together a rather nice TIG welded 29 gal fuel tank from 6061-0 for my homebuilt airplane. It's not aluminum, which I've welded, hand formed, etc. It's the application it's put to. I've seen plenty of conversions that utilized questionable approaches and/or planning. Personally, I've listened to so many RV park afternoon discussions about the current "maintenance project" that I want to see if I truly can "Do it once, do it right and never have to do it again" It may be perfectly expedient to mount an old diesel tank in a bus with bays big enough that you don't have to worry about space utilization. Especially if you don't mind doing it at more frequent intervals than expected with SS or plastic. That's simply a matter of choice and mine goes in a different direction. Onward and Upward | ||
| Chuck PD4104 Rating: N/A |
Hi Gary, You are welcome to come and visit anytime. If you do, I will be glad to show you the SS tanks in my 4104. They are commercially made SS water tanks, 16 ga, I would guess. They are held to the bus with straps, so there are no mounting fittings. The tanks are 120 gallons, or so. The waste tank's bottom rusted out, and was patched with fiberglass reinforced plastic. The fittings were put on the tank by a professional SS welder in Florida. I have the receipt. The fittings are fine, the bottom is rusted out. It's no myth! -Chuck PD4104 | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
Hi Chuck, How did the bottom rust out? Was it the weld seams and 'crevice corrosion'? Was your 4104 exposed to salt (ocean or road)? I'm just trying to pull the pieces of the puzzle together. Thanks for the info. | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
I remember you mentioning that before. You say "Rusted" out. As in red? And the bottom is rusted out, not the seams, etc? From my experience, that is truly an anomaly. Gary | ||
| Marc Bourget Rating: N/A |
Are the tanks resting on the bay floors, and, if so, were they separated/insulated from the floor? Are you truly speaking of "rust" or di-electric corrosion? (GHG's reference to salt exposure) | ||
| Russell Barnes (Neoruss)
Rating: N/A |
I spent over thirty years in the Marine field working for Mercury Outboards. In that time I saw a lot of different applications of materials. One of the most interesting was that of Stainless Steel cleats or mounting plates that were bolted to decks of boats and disintegrated. The experts opinions were that they suffered "oxygen starvation corrosion". The analysis was; "they corroded from the bottom side because they couldn't get air". I don't understand the chemistry, but I saw hundreds and there have been dozens of articles about it in marine trade mags. Perhaps your tank may have suffered this same problem if it was in contact with the floor and had water from overflow or leakage? I think the solution in boats is proper use of bedding compounds, perhaps FF knows? | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
"....was that of Stainless Steel cleats or mounting plates that were bolted to decks of boats and disintegrated....." That's crevice corosion, the presence of deoxygenated water causing a cathodic reaction. It's a form of electrolysis, more or less. Don't ask me to explain further, as a steel boat owner, I just regard electrolysis as an evil magic. Ace, I really enjoy seeing the progress you've made, you're doing a great job, I wish I could match your progress on my own. gary | ||
| Stephen Fessenden (Sffess)
Rating: N/A |
Measuring waste tank and fresh water tank level: One of the talks at Busin' 2004 was about measuring tank level. I thought it was a very simple and foolproof system. Install a tube near the bottom of the tank (from the top is fine). attach a squeeze bulb from a blood pressure cuff with a gauge. Pump air into the tube with a few squeezes. The air will begin to bubble out at the bottom and the pressure read is the depth. By the way, 1mm mercury is very close to cm water in pressure. 2.5 cm is 1 inch. So if you tank is 20 inches tall, 50mm Mercury is full, more or less. (Blood pressure is measured in mm Mercury.) You could create your own dial face for your tank. Sounded absolutely fool proof. Basic physics with no electronics. Measure tank level from inside the coach wherever you lead the line from the tube (pipe) in the tank. Just keep the bulb attached to seal the tube. I picture it located in the bathroom since that is usually right over the tanks. You cannot see through plastic tanks as they get older so that is not a good reason to use them. Who wants to see inside the black water tank? | ||
| Marc Bourget Rating: N/A |
Steve, Just for completeness, you pump until the pressure reading levels off - you don't have to either hear or see bubbles, just when you reach a maximum, correct? That, then, can be used to determine black water level, if I understand correctly? Good hint, I just think I've made my choice! | ||
| Adame Rating: N/A |
Another way is to use a very low pressure gauge like a Magnahelix, an air regulator set to a couple of psi., a dip tube in each tank connected by spaghetti tubing thru toggle valves to an air manifold. The gauge and regulated air T into this manifold. Full readings would be different for each tank based on it's depth. | ||
| Marc Bourget Rating: N/A |
Adame, I'd be reluctant to use the same guage for the fresh as the waste due to the potential for contamination! I guess you could blow through a ceramic filter like they use with some water filters, but it's a scary thought. But good idea reducing tne cost of the sensor unit. Marc | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
Back to the drawbacks of SS vs. plastic. I saw a post earlier concerning a SS tank failure and subsequent repair with fiberglass reinforced plastic. I would like to know more details about this failure. Does it support the corrosion information already posted here or does it point to another problem area? Or was it just another slam at SS tanks? Inquring minds want to know. The air bubblers for level monitors was an idea I was saving for another thread, You guys are good! | ||
| John that newguy Rating: N/A |
Same stick, just hold the other end? (huh! so that's where they got that saying from) Why aren't electrical sensors ok to use? The grommet that holds the sensor will seal, regardless of material (as long as the tank material is thick enough, that is). A common fuel tank float sender would work as well, since it would bob on top of the waste. And one of those new temperature sensing strips of the type that are used on the side of propane tanks, would work. The temperature of the liquid inside the tank will be different than the ambient temperature. And.... you can always place two, small tubing connectors, one at the top and one at the bottom of one side. Connecting clear tubing from the top to the bottom should produce a visual indication of the amount of liquid inside the tank (like one of those 40 cup coffee machines) (contents may vary) (unless it's the way my sister-in-law makes it) Flushing the tank should clean the tube as well, but it would be easily replaceable. | ||
| Marc Bourget Rating: N/A |
I understand that lug sensors corrode over, changing or reducing the amount of current to the point that the indicators are unreliable. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
Over time, the external clear plastic tubes get so that you can not see the liquid level in them. Even the ones for fresh water tanks. At least you could not in mine. I had to change then every couple of years. Richard | ||
| Jim-Bob (Pd41044039)
Rating: N/A |
While we're thinking about the 120 gallon tank hanging from the overhead, and that it weighs 960 lbs (plus the tank) full, we should get one of the engineer type guys to calculate the momentary loading that will occur when your bus goes over a huge pothole or 3" pavement dropoff, etc. That is the force that we have to engineer the mounts for. Jim-Bob | ||
| Marc Bourget Rating: N/A |
Jim-Bob, I think the same G-loading they require for propane tanks would be prudent for waste tanks. It's not full of propane but it is heavy enough to cause serious mischief! Onward and Upward. |