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Old 12-24-2015, 03:04 PM   #21
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Ok. Will wait for further discussion on this topic before removing check valve. A couple days ago I started doing what WesK says he is doing. Not sure mine will evaporate as I get about a cup of water each time I turn the water heater on. Keep in mind though, it has been cold enough here recently that I have to keep the water heater turned off most of the day to run electric heaters, stoves, etc. so when I do turn it on it is going from pretty cold to hot. Thinking the real fix would be to install a small expansion tank (smallest I have seen is 2 gl which is more than one would need) on the water heater side of the check valve. However, I don't know that anyone else is having to do this. I suspect the water heater is fairly old, but I can't imagine anything in the tank that would cause this other than the pressure relief valve, which has been replaced.

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Old 12-24-2015, 03:21 PM   #22
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I think, from your original post, you have diagnosed the problem. When you turn on the WH, the water heats and expands forcing the excess out the over temp / pressure valve. If you leave a faucet dripping, it doesn't happen as the water has a place to go. The check valve prevents the expanding water from going back into the expansion tank. Removing the check valves would appear to solve the problem. Why not try it? If your not happy with the results, you can always put it back. Think you will find that most of us don't have that check valve, I know I don't.

Ted
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Old 12-24-2015, 03:45 PM   #23
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The other reason for keeping the check valve is that if your tank runs dry the heater doesn't. This minimizes the possibility of the heater element burning in a dry tank.

I was curious enough about this to check my new-to-me boat that has a newer heater. On my boat there is a check valve and a hose running from the relief valve to the shower sump, which has a float switch controlling a small pump. The a/c drain also runs into this sump. That appears to be a simple way to keep a dry bilge.
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Old 12-24-2015, 04:00 PM   #24
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Jeff...I don't have a shower sump as it goes directly to a pump with a manual switch to dump the shower basin. In the past I have just let the water heater pressure relief valve dump into the engine room bilge, but tiring to find a way to keep the bilge dry. Sounds like a gallon jug might be the answer, although still open for suggestions.
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Old 12-24-2015, 05:18 PM   #25
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Here's how west marine suggests plumbing a potable water system on a boat:


Note the check valve installed before the water heater. In this case it also keeps city water pressure out of the potable water tank and pump.
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Old 12-24-2015, 05:23 PM   #26
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The other reason for keeping the check valve is that if your tank runs dry the heater doesn't. This minimizes the possibility of the heater element burning in a dry tank.
Ok, please explain how you think that works.

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Old 12-24-2015, 05:36 PM   #27
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Ok, please explain how you think that works.

Ted
It would but I'm not sure that's the only reason for a check valve.

Looking at the diagram above, if the potable water tank runs dry there is no pressure to empty the water heater through the faucets or shower. Water will remain in the tank.
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Old 12-24-2015, 05:44 PM   #28
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Here's how west marine suggests plumbing a potable water system on a boat:


Note the check valve installed before the water heater. In this case it also keeps city water pressure out of the potable water tank and pump.
The check valve is unnecessary as the pump has a check valve in the form of a discharge valve built into the pump. Now if you have an accumulator tank that can't handle municipal water pressure, that may be an issue.

Ted
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Old 12-24-2015, 05:51 PM   #29
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It would but I'm not sure that's the only reason for a check valve.

Looking at the diagram above, if the potable water tank runs dry there is no pressure to empty the water heater through the faucets or shower. Water will remain in the tank.
For the water which is in compressible, to drain out of the WH, you need to replace the water with air. How does the air get into the WH? If the check valve isn't there and you think the water is coming out of that inlet, where is it going (through the plumbing) and what's forcing it to flow?

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Old 12-24-2015, 06:03 PM   #30
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The check valve is unnecessary as the pump has a check valve in the form of a discharge valve built into the pump. Now if you have an accumulator tank that can't handle municipal water pressure, that may be an issue.

Ted
A quick check of accumulator tanks by Jabsco, Shurflo, Groco, and Whale showed maximum operating pressures from 100 to 125 psi.

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Old 12-25-2015, 08:49 AM   #31
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For the water which is in compressible, to drain out of the WH, you need to replace the water with air. How does the air get into the WH? If the check valve isn't there and you think the water is coming out of that inlet, where is it going (through the plumbing) and what's forcing it to flow?

Ted
Air will get into the tank when a faucet is opened.

My previous boat's water heater had a check valve built into the inlet adapter. I don't know about my current boat, where I live now I don't have to drain it.

Gravity causes water to flow downhill. That could happen in some installations.


The important thing is to follow the instructions from the manufacturer of the water heater. We don't need to ask why or second guess. RTFM!
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Old 12-25-2015, 09:25 AM   #32
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Air will get into the tank when a faucet is opened.
Most of us leave the faucet closed.

So where do you think the water is going?

Ted
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Old 12-25-2015, 09:50 AM   #33
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Before spending money try draining and refiling tank. see if that helps.
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Old 12-25-2015, 10:16 AM   #34
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Quote:
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The check valve is unnecessary as the pump has a check valve in the form of a discharge valve built into the pump. Now if you have an accumulator tank that can't handle municipal water pressure, that may be an issue.

Ted
Better to have the check valve than to rely on the one in the pump alone.
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Old 12-25-2015, 10:26 AM   #35
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If you look at the diagram, my check valve is on the other side of the T fittings for city water and faucets (just before the water tank). My water pump does have a check valve built inside it also. When we leave the boat for any time, I always try to empty my holding tank and water heater. Emptying the water heater requires me open a ball valve (installed between the check valve and water heater with a short hose to the bilge or bucket) and in order for it to drain I must open a faucet, or in most cases I just flip the lever on the pressure relief valve. It looks to me the only reason for the check valve would be to keep hot water from migrating to the cold water if the pump was turned off and you lost pressure.

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Old 12-25-2015, 10:28 AM   #36
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The West diagram stinks.

First it would require an adjustable / cleanable pressure regulator dock side.

Most water hoses are not light proof , so the green stuff will be growing all week.

It would require the prudent skipper to turn off the water on departure , even for a few hours , as a leak could easily fill the boat.

KISS , just fill the FW tank and forget about the deck fill unless its spring cleaning time and you are aboard.
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Old 12-25-2015, 10:48 AM   #37
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If boat ties into municipal water, a check valve is necessary whether in the pump or separately. If you use the tank exclusively, then no need.

The west marine diagram is flawed in the same sense as the OP's system. Only reason to have accumulator between pump and check is to protect it from higher muni water pressure. If accumulator can handle full pressure, put it on the other side of the check.
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Old 12-25-2015, 11:17 AM   #38
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Most of us leave the faucet closed.
The way we find out we are out of water is when we open the faucet and nothing comes out.
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Old 12-25-2015, 12:15 PM   #39
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The Watt's T/P valve normal operation information is available on their web site. Valve lifts at 150 psi and 210 degree's, normal to burp out a cup of water when tank is turned on. I think also standard plumbing for inlet water to have check valve to prevent back flow of hot water out of heater. If the water system is rigid, copper piped as example normal thermal expansion may cause the valve to lift. Safe practice is to manually lift the valve yearly, so burping when turned on not a bad thing. Make sure the valve discharge has a hose to prevent scalding or damage to adjacent people or equipment.
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Old 12-25-2015, 03:07 PM   #40
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I rarely use the city water hook up as I like to continually use the holding tanks to keep them fresh and clean. My boat does have a pressure regulator built into the dock side hookup.

Jerry
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