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Old 05-02-2013, 02:07 AM   #11
Join Date: Aug 2010
Location: Purcellville, VA.
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Ok, so I just now looked at the 1999 4100 SCA parts guide and they do show a check valve on the cold water side but right at the water heater. I would expect that to be on the hot side so maybe it is and the guide is just a bit off? Do you see any difference in the fittings where the hot and cold connect to the tank? This check valve (or what I have been calling a 1 way valve) should be about 2 inches long, thread into the tank and the PEX pipe should connect to it. On the other pipe, it probably just has a brass fitting instead of the valve as you need something with male threads on both ends so it can connect to the water heater and have a threaded PEX fitting connect to it.

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Old 05-02-2013, 01:26 PM   #12
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Location: Huntington, NY
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I have a 4600 SCB and my fresh water tee's directly after the pump. One feed goes to all the cold water outlets and the other goes directly into the bottom of the water heater. The top outlet of the heater feeds all the hot water outlets. Pretty simple. Assides from possibly a check valve at the input to the hot water tank, why are there any check valves? Is it possible you are feeding the hot water heater from the top and not the bottom?

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Old 05-02-2013, 01:36 PM   #13

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Originally Posted by mcoffey View Post
I don't see how an element going bad would cause this issue. I also only think these small tanks only have 1 anyway.
Yes, if you read my reply: "It kind of sounds like when the lower heating element of a standard residential hotwater heater kicks out."

Nowhere did I say there were two heating elements or that that was the problem. It sounds like what SunChaser is describing is a Pressure Storage Tank, or an Accumulator tank. Pressure storage tanks provide smooth water pressure delivery, even temperature mix in showers and reduced pump cycling. This would also explain what he is describing as getting water pressure when the pressure water pump is off.

Based on this description, I would be looking at the pressure storage tank. consider bypassing it in order to see if the problem continues or is resolved.
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Old 05-02-2013, 02:03 PM   #14

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Merged duplicate threads, so you may see the same poster with the same question about 1/2 down page one of this thread. I deleted the reply from the duplicate thread and moved the original post from the duplicate to this one.
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Old 05-03-2013, 02:17 AM   #15
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Location: Branson, MO
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Default Hot water issue

Fellow Boaters,

Please help! All of my faucets, when turned on hot, go hot - cold - hot - cold - hot - cold, and so on. It changes about every 2-3 seconds. Any clue what it might be. The water is plenty hot. This is happening on a 1999 SCA 4100 Sport Yacht. I have only had this boat 6 mos and used the hot water plumbing very little. The I know the water heater works well because the water gets really hot when any faucet is turned to hot. I am operating the system on a freshwater pump, not a city water hook up. The freshwater system has one of those pressure bulbs that has been checked and works properly. The pump is a 40 psi, I think 2.8 gpm. And I was told that it was brand new when I purchased the boat in November. The hot water and cold water goes back in fourth with the pump. When the pump cycles the water is cold and when the pump is not cycling it gets hot. I hope I have that the right way. Thanks for any and all help.


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