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Old 09-01-2015, 06:43 AM   #1
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High water pressure when water heater is first turned on?

I have been getting a burst of water pressure when I have turned the water heater on for hot water when ready to shower. This is on gas. It also does it on electric. When I go to the faucet and turn it on there is a burst of high pressure. Could the water heater pressure Valve be bad? Not to long ago I blew the bottom out of my water filter housing. Luckily I was in the camper when it happened...if it is the pressure valve how hard is that to change? I have a 2013 Forest River Flagstaff suburban water heater.


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Old 09-01-2015, 07:00 AM   #2
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Most RV or home supply stores sale pressure reducer that attach to your supply hose also the burst of high pressure from hot water is due to the fact hot water expands therefore increasing pressure.
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Old 09-01-2015, 07:15 AM   #3
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My water lines were tested at 90PSI, so I have not stayed at any park that has that high of pressure requiring a regulator. The hot water in your tank will expand and produce a but of pressure when you first turn it on. once it is relieved it should be good. As for your water canister getting blown off, if it is the FR1 with the KW1 filter there a a few known issues with these such as putting in the wrong filter or no filter at all then you tighten it too much when you do this and it breaks off the locking tabs that keep it on there.
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Old 09-01-2015, 07:32 AM   #4
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Water line pressure

No none of those I have no issues there. I have a presure regulator and the canister was ok. I am getting a burst of presure, not continual presure and only happens when water is being heated. I do not think the how water presure relief valve on heater is working properly. The hot water heater will leak a small amount on outside of camper at times
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Old 09-01-2015, 08:00 AM   #5
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If you think it is bAd, replace it.
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Old 09-01-2015, 08:04 AM   #6
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If the Temp/Pressure valve is leaking a little when the water is heated I would look more towards the temperature control first. Have you checked the water temperature after the heater is done cycling?
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Old 09-01-2015, 08:22 AM   #7
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Once the water is past the pressure relief valve into the trailer it is locked there. The water is cold. You turn your hot water heater on. As the water heats it expands increasing the line pressure. It will not go backwards out of the trailer to relieve excess pressure. You do have a safety relief valve on your hot water heater that is supposed to release high excessive pressure during the heating process. Try operating it manually a few times and make sure it is not plugged or seized. You may have to replace it.
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Old 09-01-2015, 08:35 AM   #8
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Originally Posted by fordsuperdutyE350 View Post
No none of those I have no issues there. I have a presure regulator and the canister was ok. I am getting a burst of presure, not continual presure and only happens when water is being heated. I do not think the how water presure relief valve on heater is working properly. The hot water heater will leak a small amount on outside of camper at times
Have you tried to restablish the air cushion in the water heater? Block water service to the RV, carefully bleed off water level using the heater tank relief valve until it stops flowing. Release valve handle. Now you'll have an air space for heated water to occupy without driving up pressure.
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Old 09-01-2015, 08:41 AM   #9
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If the Temp/Pressure valve is leaking a little when the water is heated I would look more towards the temperature control first. Have you checked the water temperature after the heater is done cycling?
X2 If you are water heater is leaking at times that would indicate the pressure relief valve is working. You may have a faulty temp sensor and may be letting the water get too hot.
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Old 09-01-2015, 08:56 AM   #10
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Have you tried to restablish the air cushion in the water heater? Block water service to the RV, carefully bleed off water level using the heater tank relief valve until it stops flowing. Release valve handle. Now you'll have an air space for heated water to occupy without driving up pressure.
X2 for VincwU, you need an air cushion
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Old 09-01-2015, 08:57 AM   #11
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I agree with VinceU ... you should have a small pocket of air at the top of the water heater tank that allows for expansion as the water is heated. Bleed the water down a bit and see what happens next heating cycle. The pressure relief valve at the top of the heater tank may seep just enough to let the air cushion out. It's easy to replace if need be.
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Old 09-01-2015, 11:52 AM   #12
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I think a pressure regulator should aways be used. Rv systems are safest around 50 psi and "city water" , park water is often higher than that. Pressure regulator should be at the faucet to keep excess pressure off the hose. The surge you described can be from any of three causes that I can think of right now. Expansion in the hose building up either because of no regulator or the regulator being after the hose, at the coach or inside. Expansion of too big an air pocket in the top of the water heater, which can be relieved by the tab on the pressure relief valve. Or maybe worst case expansion in the hot water lines from chronically high water pressure. The latter could have you dangerously near a catastrophic failure. SO, IN EVERY CASE, use a pressure regulator and NEVER leave the coach with water turned on or water pump left on. Good luck. Please let us know what solves your problem.
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Old 09-01-2015, 12:40 PM   #13
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The small burst of slightly higher pressure from the hot tap after the water heater has cycled the first time is normal. Whenever you heat something, it expands creating higher pressures. What is not normal is a constant drip or discharge from the water heater temp/pressure relief valve. Some discharge at times is normal. From your description this is what you have, but if you want continue on. Yes, please do check the temperature of the hot water after the heater has cycled. If it is higher than 120 deg you risk burns and at some point the relief valve will start to relieve. They are usually set to go off at 210 deg F and I think 150psi. Long before those values they will start to open a little. Yes please do allways use a pressure regulator on the incoming line, it's a surge arrestor for the water line. No please do not put an air cushion in your water tank, it will disappear. Water is nothing more than oxygen and hydrogen, air will get absorbed and there goes your air cushion. If you want to do something permanent, install a small expansion tank by your water heater on the cold line. Such as a Watts PLT-5. And yes getting the temp/pressure relief valve out is a b***h. They run them in tighter than tight with air tools before the heater is installed. Once it's installed it's recessed so it's even more difficult. Getting it out usually takes a basin wrench. All that being said, from your description I would not worry.
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Old 09-01-2015, 03:42 PM   #14
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For an RV with 6 gallon water heater this will fix the surge after water heats up: Amazon.com: SHURflo 182-200 Pre-Pressurized Accumulator Tank: Automotive
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Old 09-01-2015, 07:07 PM   #15
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Originally Posted by fordsuperdutyE350 View Post
I have been getting a burst of water pressure when I have turned the water heater on for hot water when ready to shower. This is on gas. It also does it on electric. When I go to the faucet and turn it on there is a burst of high pressure. Could the water heater pressure Valve be bad? Not to long ago I blew the bottom out of my water filter housing. Luckily I was in the camper when it happened...if it is the pressure valve how hard is that to change? I have a 2013 Forest River Flagstaff suburban water heater.


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Question? When you hooked up the hose and turned the water did you bleed off the air at the water relief valve if not that is where the air is comming from once that gone should work fine.
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Old 09-01-2015, 07:14 PM   #16
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For an RV with 6 gallon water heater this will fix the surge after water heats up: Amazon.com: SHURflo 182-200 Pre-Pressurized Accumulator Tank: Automotive
Have one of those. PRICELESS. HOT OR COLD saves a lot of cycles on the pump.

However, not likely to cure this original problem. Air in the system will eventually bleed out. Too much air pocket could fry the electric WH element first, but will eventually bleed out. And an over active WH would not pressurize only the hot as it would back pressure up in to the cold feed line as well. SOOO seems to me to come down to too much pressure and maybe just more notable on the hot side--- cause IT'S HOT. Get a regulator on the city/park faucet and see what results.
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Old 09-02-2015, 08:30 AM   #17
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The small burst of slightly higher pressure from the hot tap after the water heater has cycled the first time is normal. Whenever you heat something, it expands creating higher pressures. What is not normal is a constant drip or discharge from the water heater temp/pressure relief valve. Some discharge at times is normal. temperature of the hot water after the heater has cycled. If it is higher than
120 deg you risk MOST UNITS COME FROM FACTORY 130-140 F RELIEF VALVES ARE SET TO 135 PSI
burns and at some point the relief valve will start to relieve. They are usually set to go off at 210 deg F and I think 150psi. Long before those values they will start to open a little. Yes please do allways use a pressure regulator on the incoming line, it's a surge arrestor for the water line. No please do not put an air cushion in your water tank, it will disappear.
WATER AND AIR ARE INSOLUABLE, DIVERS BUBBLES RISE TO THE TOP. THERE IS A GOOD REASON RV WATER HEATERS OUTLET IS TAPPED ABOUT 25% FROM THE TOP, ALLOWS AIR SPACE, SAME FUNCTION AS A ACCUMULATOR. NOTE HOME HEATERS TAP THE TOP OF THE TANK, NO AIR SPACE.
Water is nothing more than oxygen and hydrogen, air will get absorbed and there goes your air cushion. If you want to do something permanent, install a small expansion tank by your water heater on the cold line. Such as a Watts PLT-5. And yes getting the temp/pressure relief valve out is a b***h. They run them in tighter than tight with air tools before the heater is installed. Once it's installed it's recessed so it's even more difficult. Getting it out usually takes a basin wrench. All that being said, from your description I would not worry.
DISAGREE WITH SOME OF YOUR POINTS. The aircushion is designed in by Atwood and Suburban otherwise they would tap the tank top for more volume.
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Old 09-02-2015, 09:18 AM   #18
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air expansion

sounds like you have a pocket of air in your tank. try releasing your pressure release valve for a few seconds and see if any air escapes.
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Old 09-02-2015, 09:28 AM   #19
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DISAGREE WITH SOME OF YOUR POINTS. The aircushion is designed in by Atwood and Suburban otherwise they would tap the tank top for more volume.
You either bleed off the air at the pressure valve until it all water or the faucets one way or another the air will come out!!!!!!!!!!!!!!!!!!!!!
so it is so it does whether you think so or not i've deen doing this for a long time it doesn't keep the ht from haveing the expansion it needs!!!!
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Old 09-02-2015, 09:36 AM   #20
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X2 for VincwU, you need an air cushion


yOU DON'T LOOSE THE air cushion if you bleed off excess air either you do it at the pressure valve or the faucets one way or the other!!!!!!!!!!!!!!!!!!!
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