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Old 21-01-2021, 10:06   #1
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Water heater install plumbing question

Hi All,
I'm in the process of installing a 15 litre, 120v water heater on my sailboat. I do not have a pressurized water system but instead will use a 12v pump on a momentary switch, same set up as my cold fresh water system. Water will be delivered to the sink through a hose attached to a simple tube which will have no faucet on it. My question is does the water heater need a faucet to hold in the heat/pressure? With a simple open tube set up will the hot water want to naturally squirt out the tube as it heats up and expands?


Cheers and thanks for any feedback.


JC
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Old 21-01-2021, 10:22   #2
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Re: Water heater install plumbing question

As any liquid heats, it expands. If you have an open tube at the end with no valve, it'll run out as it expands. This may lead to another issue where siphoning may eventually drain the heater tubes and it'll go dry.

Adding a ball valve under the sink isn't that difficult if you don't want to put a faucet on there.
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Old 21-01-2021, 14:49   #3
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Re: Water heater install plumbing question

Rob P gave you excellent advice. If you look on any water heater you will see an over pressure / over temperature relief valve. If you have no faucet or valve the expansion has to go somewhere. When it’s cold out and we haven’t sent any electricity to the water heater during the night and I get up and fire up the hydronic system or start the generator and the water heater goes from cold to hot...opening the faucet shows you how fast pressure will build up. Kinda like the warning on your car radiator...do not open when hot...not exactly but similar.
As Rob suggested, a simple 1/4 turn ball valve will do. Just remember if you are working near your engine or water heater, if it’s hot, it can hurt you.
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Old 21-01-2021, 15:12   #4
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Re: Water heater install plumbing question

Why not just install a pressure pump and a faucet?? Neither are very expensive. The pressure pump would be right after the water tank and feed both the cold and hot sides.
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Old 22-01-2021, 11:59   #5
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Re: Water heater install plumbing question

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Originally Posted by Shrew View Post
Why not just install a pressure pump and a faucet?? Neither are very expensive. The pressure pump would be right after the water tank and feed both the cold and hot sides.
Have you considered a tankless system? You only need one pump for both your hot and cold.
Amazon do them for boats for $360

https://www.amazon.com/WATER-HEATER-...1341862&sr=8-5
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Old 22-01-2021, 14:31   #6
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Re: Water heater install plumbing question

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Originally Posted by sengland View Post
Have you considered a tankless system? You only need one pump for both your hot and cold.
You should only need one pump for any marine water heater.
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Old 22-01-2021, 14:35   #7
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Re: Water heater install plumbing question

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Originally Posted by jooa View Post
Hi All,
I'm in the process of installing a 15 litre, 120v water heater on my sailboat. I do not have a pressurized water system but instead will use a 12v pump on a momentary switch, same set up as my cold fresh water system. Water will be delivered to the sink through a hose attached to a simple tube which will have no faucet on it. My question is does the water heater need a faucet to hold in the heat/pressure? With a simple open tube set up will the hot water want to naturally squirt out the tube as it heats up and expands?


Cheers and thanks for any feedback.


JC
I would add pressure water. Not expensive and the one pump will feed both hot and cold sides. Installed after the tank but before anything else. You do need a non-return valve so the hot water doesn't flow into the cold side.
A Jabsco or similar pump with pressure switch is under $200.

What water heater are you installing?
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Old 22-01-2021, 14:41   #8
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Re: Water heater install plumbing question

The water coning out of the water heater could be dangerously hot, you might consider a thermostatic valve, though all of this will be a bit tricky without a pressurized water system.

Is there a reason you don't want to add a pump and a simple faucet?
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Old 22-01-2021, 23:29   #9
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Re: Water heater install plumbing question

Thanks for all the advice, The reason I'm not crazy about installing a pressurized system is I have very limited tankage, only have 60L capacity (27' boat) and from what I've heard from all my friends who have pressurized systems is they do waste more water. This is also the reason I didn't install a tankless heater because there is more water wastage before hot water arrives, I also didn't want to deal with exhaust involved with a propane setup. I'm installing an Eccotemp undersink water heater ($217.00 Canadian). It's not a totally marine unit but they do advertise they can be installed in RVs and boats and the unit is pretty compact. Talking with friends it made sense to install the 15L version because the water most likely would stay warm until the next morning. The idea of installing a ball valve seems like a pretty simple and inexpensive solution and I will do that for the time being. Installing check valves on both the hot and cold also makes sense. If it doesn't work out then I will rethink the idea of going to a pressurized system. I'm in the middle of a galley rebuild and am trying to fit in extra tankage for the water heater.

Thanks again for all the good advice!
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Old 23-01-2021, 00:34   #10
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Re: Water heater install plumbing question

JC

What are the options you are considering for extra water tanks?

Curious as I have a CS27 as well.
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