HPHT Valve Replacement

[johnleann]

I believe I need to change out the High Pressure High Temp valve on my water heater. It is fine when under pressure from city hookup or water pump, but leaks when it is heated.
Are these valves universal in that I can go to the hardware store and get another to replace it or are they specialized? Special thread size?

Thank you.

[Herk7769]

Depending on your model it could be 1/2 inch NPT or 3/4 inch NPT.

water Heater Temperature and Pressure Relief Valve, 3/4 - $12.89

water Heater Temperature and Pressure Relief Valve, 1/2 - $13.99

For some idea of prices.

[johnleann]

I replaced my High Temp High Pressure valve yesterday after work. It is 3/4 npt valve with the teflon already on the threads. It was fairly easy and straight forward operation. Had to bring the trailer over from storage yard about 2 blocks from house, opened hot faucet in bathroom and relief valve. Removed the anode rod and the tank drained great. There were fresh deposits on it so it is working. Changed it in May. Removed the heat shield for better access to the valve and when it was out by the use of a big crescent wrench, I flushed the tank through the valve fitting. Lots of rust and some more debris came out of the anode hole.

Put it all back together and it was going well. Hooked up the house water to the city connection and filled the tank until water came out of the bathroom faucet. No leaks. Lit the water heater and waited for it to come to temp and shutoff.
Well before it reached temp, the new valve LEAKED TOO. It is a high temp valve after all and it does seem at times that the water is too hot. On the inside door of the wh cover is a sticker saying that 'weeping' is a normal occurrence of water heating and expansion. I think that this is excessive though.

Could the thermostat be faulty? Looks like there is t-stat on the lower left front under circular black plastic cover. How do I go about testing the t-stat? I saw on a RV DIY website that there are adjustable t-stats. Maybe I should try to locate one of the adjustable types and be done with it.
Suburban water heater btw.
Thanks for reading long post.

[Witch Doctor]

Originally Posted by johnleann

I replaced my High Temp High Pressure valve yesterday after work. It is 3/4 npt valve with the teflon already on the threads. It was fairly easy and straight forward operation. Had to bring the trailer over from storage yard about 2 blocks from house, opened hot faucet in bathroom and relief valve. Removed the anode rod and the tank drained great. There were fresh deposits on it so it is working. Changed it in May. Removed the heat shield for better access to the valve and when it was out by the use of a big crescent wrench, I flushed the tank through the valve fitting. Lots of rust and some more debris came out of the anode hole.

Put it all back together and it was going well. Hooked up the house water to the city connection and filled the tank until water came out of the bathroom faucet. No leaks. Lit the water heater and waited for it to come to temp and shutoff.
Well before it reached temp, the new valve LEAKED TOO. It is a high temp valve after all and it does seem at times that the water is too hot. On the inside door of the wh cover is a sticker saying that 'weeping' is a normal occurrence of water heating and expansion. I think that this is excessive though.

Could the thermostat be faulty? Looks like there is t-stat on the lower left front under circular black plastic cover. How do I go about testing the t-stat? I saw on a RV DIY website that there are adjustable t-stats. Maybe I should try to locate one of the adjustable types and be done with it.
Suburban water heater btw.
Thanks for reading long post.

Your stat which I'm pretty sure is just to disk that contact the heater wall, make sure the area of contact is clean and tight against the body. They are pre set. The only way you can tell would be to open a faucet fill it with hot water ans see the temp. then go outside with a meter and see if it is still getting juice. You do need to find out the degree the temp sensor shuts off at. Remember it is only metal touching metal so any dirt or not being tight against the wall will cause it to stay on longer......

[OldCoot]

Stand to the side and flip the valve several times to clear it of any debris. Sometimes it take 5 or 6 times to get it to seat properly. It only takes a very small pc of mineral deposit to keep the valve from seating.

[johnleann]

Thanks for the tip on checking the contact area of the stat. Maybe tomorrow.

The valve only leaks when it is heated up, but I did get more junk out of the anode hole when I flushed it. Possible more junk still in there but I did not flip the valve at anytime after install.

[johnleann]

From Suburban Water Heater manual
Seeping/Dripping
If the pressure relief valve on the back of the water heater seeps or drips water, you may have lost the air pocket that is normally present at the top of the water heater. This can occur over time.
To re-establish the air pocket, follow these steps.
1. Shut off the water heater (LP and electric)
2. If using city water, turn off the faucet. If on internal water, turn off the pump.
3. Open a hot water faucet in the RV.
4. Carefully open the pressure relief valve and allow water to flow out until it stops flowing.
5. Let the pressure relieve valve snap back to the closed position.
6. Close the hot water faucet and turn on the water supply.
7. Turn the water heater on and check for normal operation.
If the seeping/dripping continues, the pressure relieve valve is probably defective.

[Herk7769]

Additionally, you CAN get a bad one right out of the box.

[w4drr]

Originally Posted by johnleann

From Suburban Water Heater manual
Seeping/Dripping
If the pressure relief valve on the back of the water heater seeps or drips water, you may have lost the air pocket that is normally present at the top of the water heater. This can occur over time.
To re-establish the air pocket, follow these steps.
1. Shut off the water heater (LP and electric)
2. If using city water, turn off the faucet. If on internal water, turn off the pump.
3. Open a hot water faucet in the RV.
4. Carefully open the pressure relief valve and allow water to flow out until it stops flowing.
5. Let the pressure relieve valve snap back to the closed position.
6. Close the hot water faucet and turn on the water supply.
7. Turn the water heater on and check for normal operation.
If the seeping/dripping continues, the pressure relieve valve is probably defective.

That is exactly right. Once you lose the air bubble at the top of the tank, whenever it heats up, the water expands, and without that air bubble it has no where to go and pressure builds quickly, causing the relief valve to do it's job. Restore the air bubble and see if the leak stops.

Bob

[OldCoot]

Originally Posted by w4drr

That is exactly right. Once you lose the air bubble at the top of the tank, whenever it heats up, the water expands, and without that air bubble it has no where to go and pressure builds quickly, causing the relief valve to do it's job. Restore the air bubble and see if the leak stops.

Bob

I do believe the pressure is the same with or without the air bubble.

[w4drr]

Originally Posted by OldCoot

I do believe the pressure is the same with or without the air bubble.

Water cannot be compressed. Without somewhere to expand to easily (air bubble), pressure will build high enough to stretch the water heater and the rigid PEX lines if necessary, if it wasn't for the relief valve. I have seen this pressurization effect many times when the water heater is heating up, and the heater has lost it's air bubble, particularly if it is heating from a cold start. Of course, running a little hot water now and then while the tank is heating helps to bleed off this pressure. Usually, unless I forget, I do the air bubble restore trick before each trip, as the bubble apparently disappears fairly quickly.

Bob

[OldCoot]

Originally Posted by w4drr

Water cannot be compressed. Without somewhere to expand to easily (air bubble), pressure will build high enough to stretch the water heater and the rigid PEX lines if necessary, if it wasn't for the relief valve. I have seen this pressurization effect many times when the water heater is heating up, and the heater has lost it's air bubble, particularly if it is heating from a cold start. Of course, running a little hot water now and then while the tank is heating helps to bleed off this pressure. Usually, unless I forget, I do the air bubble restore trick before each trip, as the bubble apparently disappears fairly quickly.

Bob

I agree water cannot be compressed, but I will stand by my statement that the pressure remains the same regardless of the presence of the air bubble. The water pump/city water/pressure regulator doesn't know or care about the air bubble.

The air bubble just keeps the water away from the valve.

[w4drr]

Originally Posted by OldCoot

I agree water cannot be compressed, but I will stand by my statement that the pressure remains the same regardless of the presence of the air bubble. The water pump/city water/pressure regulator doesn't know or care about the air bubble.

The air bubble just keeps the water away from the valve.

Because of the inlet check valve, the pressure in the tank cannot bleed back to the city water/pump side. The only direction it can go is out the hot outlet side of the tank. If no hot water valves are open in the camper, then pressure builds.

Bob

[OldCoot]

Originally Posted by w4drr

Because of the inlet check valve, the pressure in the tank cannot bleed back to the city water/pump side. The only direction it can go is out the hot outlet side of the tank. If no hot water valves are open in the camper, then pressure builds.

Bob

And builds and builds and builds and .