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New Suburban SW6D water heater T&P valve leaks, HELP!!


Dabbs
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Hello everyone, newbie here but long time camper owner... 

My 27 year old Suburban water heater finally sprung a leak in the tank so had to replace it, bought a brand new identical one mainly for easier install. Problem is the T&P (pop off) valve on the new one leaks during heating cycle, not the threads but through the valve itself. I tried a replacement valve but it does the same thing, it's about a drop every two seconds for at least 15 minutes. Seems like when it gets up to temp and the flame goes out it stops dripping....

These valves are rated 150psi and 210*, I tested the water temp at 142* so not near the 210*. I haven't figured out how to test the pressure but I would think if it's 150psi it would blow my rv lines? 

Surprisingly the manual has a section for 'water weeping' through the valve, it says to shut off the water supply then open the T&P valve til it stops flowing to create a bigger air pocket to allow for pressure. I've done that numerous times but it still drips, I'm at a loss. Do all of these new water heaters leak through the valve like this? I just can't believe they do, Help and Thanks 

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Welcome to the Escapee forums!

Have you left an air bubble in the top of the water heater? If you don't the expanding water has to exit or it would burst your new tank.

You can put an air bubble into the tank by opening the relief valve with the lever and draining out a small amount of water from the how water, low point drain. When you close the valve, snap it shut rather than easing it as it is designed to seat that way. 

Edited by Kirk W
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A different, simple way to introduce air into your water heater is to take an empty water hose, hook it up to your city water inlet, and then turning on the water hydrant. Once you've done that, open a hot water faucet in the RV (very important, do not open a cold water faucet!). 

The air in the hose will bubble and gurgle it way into the water heater.  You should get some sputtering out of the hot water faucet to let you know that you've got an adequate bubble.  If you don't, empty the hose and repeat.

While it is possible that you've got a faulty T&P valve, it is more likely that you need to establish this bubble.  If opening the T&P valve hasn't worked, give this method a try. I find it works well. 

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DO NOT open the safety and temperature valve with water pressure applied or you may get(normal temp = 190°) someone scalded. First turn off water supply, open kitchen faucet to eliminate pressure in the system, THEN open safety and temperature valve and allow all water to drain out. Snap closed afterwards.

Edited by Ray,IN
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Yes I've done that a dozen or so times now, safely like Ray says too. Still weeps while the flame is on, seems so ridiculous to have to go through all of this with a brand new water heater. I've had many campers in my life, some new some old that never acted like this...... It's got me weeping too:angry:  

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Ha, drip chain? That's a neat idea, I was going to do the drain tube thing but decided that's just not a proper fix and I shouldn't have to put up with a weeping water heater that's brand new. There's got to be something I'm missing because not every other water heater out there weeps....

So I went back to square one on how these things are designed to create an air pocket, upon my research I found they have an inner diverter pipe (plastic I think) in the top hot outlet port. This diverter pipe is a distance from the top of the tank, when filling the tank the water will exit that pipe before the tank is full thus creating an adequate air pocket. If that pipe has a breach then water would completely fill the tank resulting in no air pocket, under normal conditions the tank does build up pressure but since air compresses the valve doesn't open....

I believe this heater has a defective diverter pipe so I'm going to return it for another new one, it's the only solution that makes sense to me 

 

 

water heater cut-out.jpg

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The reason the T&P valve leaks while the water heater is heating water is water expands when heated.  The reason the water escapes the T&P valve is because you have a closed water system on the RV, and regardless if you are connected to external water with a hose or just working with fresh water in your onboard tank, the water expands and has nowhere to go except out the T&P valve, which is what you want so your plumbing doesn't explode.  The air pocket at the top of the water heater tank will allow for the expansion and should stop the water from seeping out the valve.  There is another option, and that is to install an accumulator tank, such as one of these https://www.amazon.com/SHURFLO-182-200-Pre-Pressurized-Accumulator-Tank/dp/B000N9VF6Q/ref=sr_1_3?dchild=1&keywords=rv+water+accumulator+tank&qid=1619397854&sr=8-3

This would be installed in the cold water side of your water system, and then when the water heater is heating, this tank will absorb the expansion, so you wouldn't need to worry about the air pocket in the water heater tank.  Your water heater and the T&P valve are working exactly as they are designed and you will not be able to keep replacing water heaters to find one that doesn't relieve water pressure like they are supposed to.

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On 4/22/2021 at 11:24 AM, Dabbs said:

Ha, drip chain? That's a neat idea, I was going to do the drain tube thing but decided that's just not a proper fix and I shouldn't have to put up with a weeping water heater that's brand new. There's got to be something I'm missing because not every other water heater out there weeps....

So I went back to square one on how these things are designed to create an air pocket, upon my research I found they have an inner diverter pipe (plastic I think) in the top hot outlet port. This diverter pipe is a distance from the top of the tank, when filling the tank the water will exit that pipe before the tank is full thus creating an adequate air pocket. If that pipe has a breach then water would completely fill the tank resulting in no air pocket, under normal conditions the tank does build up pressure but since air compresses the valve doesn't open....

I believe this heater has a defective diverter pipe so I'm going to return it for another new one, it's the only solution that makes sense to me 

 

 

water heater cut-out.jpg

Sounds good. I was thinking your pop off valve has a bad gasket. You tried to create a air pocket several times and it didn't hold it.

Welcome to the forum.

Bill

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Before I retired I bought and sold hundreds, maybe thousands of T&P valves. The fact that it stops weeping after the water reaches temp means that it has nothing to do with the air bubble. The fact that you already tried a replacement eliminates a defective valve. I would find out who a regional Watts distributor is and call them. Not a retailer but the distributor.

Tell them it weeps and then stops, see what they say.

Its way easier that removing and reinstalling another water heater.

Let us know........

Bob

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19 hours ago, 57becky said:

The reason the T&P valve leaks while the water heater is heating water is water expands when heated.  The reason the water escapes the T&P valve is because you have a closed water system on the RV, and regardless if you are connected to external water with a hose or just working with fresh water in your onboard tank, the water expands and has nowhere to go except out the T&P valve, which is what you want so your plumbing doesn't explode.  The air pocket at the top of the water heater tank will allow for the expansion and should stop the water from seeping out the valve.  There is another option, and that is to install an accumulator tank, such as one of these https://www.amazon.com/SHURFLO-182-200-Pre-Pressurized-Accumulator-Tank/dp/B000N9VF6Q/ref=sr_1_3?dchild=1&keywords=rv+water+accumulator+tank&qid=1619397854&sr=8-3

This would be installed in the cold water side of your water system, and then when the water heater is heating, this tank will absorb the expansion, so you wouldn't need to worry about the air pocket in the water heater tank.  Your water heater and the T&P valve are working exactly as they are designed and you will not be able to keep replacing water heaters to find one that doesn't relieve water pressure like they are supposed to.

Nope an accumulator tank is locked out of the hot water side of RV plumbing by a backflow preventer valve on the cold water inlet of the water heater to prevent how water from expanding into the cold water system.

ref: https://blog.goodsam.com/rv-doctor-basic-rv-water-system-check-valve-placement/

You should see this valve in your cold water plumbing to your water heater:https://www.amazon.com/rv-water-heater-check-valve/s?k=rv+water+heater+check+valve

Edited by Ray,IN
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38 minutes ago, Ray,IN said:

Nope an accumulator tank is locked out of the hot water side of RV plumbing by a backflow preventer valve on the cold water inlet of the water heater to prevent how water from expanding into the cold water system.

That is true if the check valve is on the cold side but they are on the hot water outlet side on some units. My current RV has one on the hot side. The same was true of the motorhome that we used to have and I did put in an accumulator, partly for that reason. 

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5 hours ago, Kirk W said:

That is true if the check valve is on the cold side but they are on the hot water outlet side on some units. My current RV has one on the hot side. The same was true of the motorhome that we used to have and I did put in an accumulator, partly for that reason. 

I've seen a check valve on both a time or two, my present one does, usually on cold side from factory. It doesn't hurt for hot water to expand into hot water plumbing lines they are designed for hot temperatures. Blue PEX is for cold water red for hot.

That makes me wonder if the accumulator tank bladders are designed to withstand 140°F?

Edited by Ray,IN
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If there is not a check valve in the cold water entrance port of the water heater, the accumulator tank will keep internal water heater tank pressure from exceeding the setting of the T&P valve.  PEX tubing, whether it is white, blue, or red is all the same and is rated well above the 140 degrees of most water heaters in these RV's.   The color is just there to aid in the installation and future maintenance so it is easy to identify which is hot or cold.  This is the specs for PEX from the Lowe's site, and this applies to all colors of PEX:

  • Minimum working temperature 33 degrees F at 160 PSI

  • Maximum working temperature 200 degrees F at 80 PSI

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10 hours ago, Ray,IN said:

That makes me wonder if the accumulator tank bladders are designed to withstand 140°F?

If the accumulator is installed at the outlet of the water pump, as most are, it will still maintain pressure on the entire cold water system, and never see any hot water. I suppose that it could be exposed to hot water is connected directly at the water heater, but I have never seen it done that way. I have put them in 3 different RVs and always near the pump. 

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  • 8 months later...

I was having the same issue with our suburban 6gal hot water tank in our keystone 5th wheel brand new as of 2019, from day one. Followed all the correct processes to re-establish the air pocket to no avail. Even changed the t&p valve. Our hot water tank did not have a backflow preventer on the cold water side of the hot water tank. I called suburban about the issue and they recommended I install a accumulater tank on the cold water side on the hot water tank, so I did,.and no more T&P relief valve dripping during heating cycle. If you contact suburban they will suggest this if you have tried the normal process to re-establish the air pocket and it doesn't work.

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