| Author | Message | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 207 Registered: 2-2004 Posted From: 75.53.31.102 Rating: N/A |
When I heat my water there is no provision for expansion and it forces water out the T&P valve on the water heater. I have a check valve downstream the Flowjet bladder tank. I have to have this to keep water from running backwards through the Flowjet and overfilling my water tank when hooked up to RV park faucet pressure. This is the same kind of problem you see the guys fix on "Ask This Old House" where because a backflow preventor is installed on a plumbing system, the hot water has no place to expand, thus dripping out the T&P valve. There is no room to put the check valve upstream the expansion tank and downstream the Flowjet as the foot print of the package unit is too tight. It is the system that Camping World sells, so if you've seen one you understand what I'm saying. I could put a small air chamber adjacent to my shower valve. This would be the highest point in the plumbing system and relatively easy to access. My question, would it work, and how big should it be? Any ideas? Thanks, David (Message edited by davidanderson on July 10, 2007) (Message edited by davidanderson on July 10, 2007) | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 627 Registered: 10-2003 Posted From: 71.58.117.21 Rating: N/A |
could you install a small expansion tank teed into hot water line just off heater? precharge ir with some air pressure with a tire stem type fitting? | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1108 Registered: 5-2001 Posted From: 65.74.67.130 Rating: N/A |
David, I understood that the water heater was supposed to have some expansion room in it. Did you find that there isn't any? Thanks. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 393 Registered: 11-2005 Posted From: 63.97.117.53 Rating: N/A |
David, As Tom said, there is supposed to be air in the top of the water heater. Make sure the plug is in and the valve is closed before you charge the water heater with water, that way you will have air at the top. I have no expansion tank or pipe on my 4104 and never have any problem. Yoyr popoff valve may just have a leak. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 223 Registered: 8-2006 Posted From: 207.231.81.59 Rating: N/A |
Dave, I don't have the exact number, but I believe that a 50 gallon heater heating water 100 degrees will expand about 3 quarts. Remember that you cannot compress a liquid, period! If you put a gauge on your water system, and turn on the heater, you will see the pressure rise to the relief valve setting, when it starts to drip. The pressure will stay there until water is used, when it will drop immediately to the pump or city water pressure. #1, This is really hard on your water heater, and may well cause a flex connector or a plastic valve to fail with disastrous consequences, if your are gone and hooked up to city water, or left the pump switch on!!! #2, The TP valve will soon fail to seat properly, and leak continuously. This must be corrected quickly! I can't "see" your plumbing schematic, but I will offer two suggestions. One is to somehow move the check valve so it doesn't prevent the heater's cold water from backing into the flowjet tank, which it should. You should be able to do this with a little re-plumbing, just tee the shore water in so that you have: storage tank, pump, check valve, city water tee, bus cold tee, pressure tank tee, and water heater cold supply on the other side of the pressure tank tee. The pressure switch should be near the Flowjet tank if possible. If your pressure switch is built into your pump, put the check between the pump and the storage tank. Try and take the bus cold water connection out on the pump side of the pressure tank, so it doesn't get warm water from the heater expansion. The second option is to install a bladder-type expansion tank common to the heater. Set the air precharge equal to the pump cut-out pressure. I am personally not familiar with any water heaters that are equipped with expansion capabilities? Well, I'm too wordy again, and another post has gotten in, so. Air in a water heater will cause damage where the air is, as it will overheat if common to the fire. Secondly, air won't stay in a heater, as the outlet is designed to take the hottest water off the top. Height of the tank doesn't matter, and an air chamber doesn't have enough capacity, and quite often becomes waterlogged. Gus's system works fine because he doesn't have a check between his heater and his pressure tank, as most of us don't! George (Message edited by George Mc6 on July 10, 2007) | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 440 Registered: 7-2006 Posted From: 66.217.106.105 Rating: N/A |
David - Unless I'm misunderstanding your problem, I'm going to add a "ditto" to Tom and Gus' comment. When you fill the system, the "TP" valve must be closed. Doing so will leave enough room at the top of the tank for expansion. If the valve leaks, it should be replaced, since: A. It will eventually fail B. It will allow the tank to eventually fill beyond the manufacturer's recommended limit, and will cause the tank to purge through the valve when the water expands. The tank's instruction booklet should clearly state all that.... | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 208 Registered: 2-2004 Posted From: 75.53.31.102 Rating: N/A |
The heater is a Seaward 10gal. If it is similar to a house type system the hot water leaves the tank at or near the top, thus no air stays in the tank as George wrote above. A small bladder tank could be installed adjacent the water heater, but my question, how big? How does the industry size these things? Replumbing the check valve at the Flojet delivery pump would be difficult because of space. A remote expansion tank is much more doable. Using George's formula of 50 gals + 100 degree rise = 3 quarts, then 10 gals would be .20 x 3 quarts = .6 quarts bladder capacity (assuming 100 degree rise) That is a lot of rise. That would be 40 degree incoming heated to 140. Wow, that is a lot. Am I on the right thought for sizing? Thanks, David | ||
| Chris Peters (Chris_85_rts)
Registered Member Username: Chris_85_rts Post Number: 34 Registered: 11-2006 Posted From: 66.194.150.45 Rating: N/A |
Go to home depot, they sell exactly what you are looking for. A hot water heater expansion tank. They are relatively small, a few gallons at best, and as I recall there is only one size. I used one for two reasons, hot water expansion, and to keep the pump from cycling constantly. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 176 Registered: 7-2006 Posted From: 4.240.213.116 Rating: N/A |
Kinda tough to read red, David...  ...at least for more "mature" eyes... RCB | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 209 Registered: 2-2004 Posted From: 75.53.31.102 Rating: N/A |
Sorry about that RCB. I'll stick with blue or purple. How about green? I know that yellow is really bad I like to post in a different color so I can find my posts easily from the default black. David | ||
| Chuck Newman (Chuck_newman)
Registered Member Username: Chuck_newman Post Number: 202 Registered: 1-2005 Posted From: 63.145.177.245 Rating: N/A |
Chris, Tell me more about your HD hot water expansion tank. How big is it? Relative to pump cycling, does this expansion tank do the same job as an accumulator tank in the cold water line down stream from the pump? If so, then based on the above discussions, I am correct that the only check valves in the system should be at the output of the pump, and at the city water inlet? | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 211 Registered: 2-2004 Posted From: 75.53.31.102 Rating: N/A |
Thanks for the input, guys. A search for a small bladder tank is in my future. I don't know when I'll be able to get this done, but when I do I'll post the results. David | ||
| Chris Peters (Chris_85_rts)
Registered Member Username: Chris_85_rts Post Number: 35 Registered: 11-2006 Posted From: 66.194.150.45 Rating: N/A |
Chuck, I did not buy the pump with the built in accumalator tank, purchasing it separately was less expensive at the time. I have a well water system in my home, so I modeled this system off of it. The HD expansion tank is exactly the same as an accumulator tank, just smaller. It is plumbed in my system on the cold water output for the pump. At this time I have added no check valves, so I suppose I can get a little hot water bleed back into the cold pipes. My city water inlet is a combo check/regulator. In reading the above, I suppose I should have added a check valve to the output of the pump to provide redundant protection to the pump. With the accumulator charged with air at the low cut off, I can get several minutes of water out a sink faucet before the pump kicks on. Pics at: http://www.flickr.com/photos/79505093@N00/sets/72157600858590579/ (Message edited by chris 85 RTS on July 16, 2007) |