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Old 02-01-2016, 12:03   #1
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Hot Spigot produces cold, then hot, then cold etc.

My hot water heater works fine as does my water pump. However, in the past few weeks (with no changes to either) the hot water spigot produces cold, then hot, then cold, then hot, etc. etc. back and forth.

I did notice that when my water pump kicked in that the hot kicks to cold and the cycle begins all over.

Thanks in advance for any suggestions!

Rick
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Old 02-01-2016, 12:35   #2
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Re: Hot Spigot produces cold, then hot, then cold etc.

Quote:
Originally Posted by rwells36 View Post
My hot water heater works fine as does my water pump. However, in the past few weeks (with no changes to either) the hot water spigot produces cold, then hot, then cold, then hot, etc. etc. back and forth.

I did notice that when my water pump kicked in that the hot kicks to cold and the cycle begins all over.

Thanks in advance for any suggestions!

Rick
Do you have a single faucet that mixes hot and cold water, or separate faucets for hot and cold water?

If the former, it could be that the mixer is mixing a bit of cold water with the hot water, and when the pump comes in the proportion of cold water increases significantly. Try closing the flow of cold water into the faucet and you will find out if this was the problem.

There could be a blockage in the hot water line (which makes th eproiportion of cold water increase when pressure goes up.

Do you have an accumulator tank? If so then when it stops working you will find more variation in temperature (mechanism above) as pump cycles in and out.
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Old 02-01-2016, 13:14   #3
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Re: Hot Spigot produces cold, then hot, then cold etc.

I have both types of faucets on the boat; same issue with both kind. I drained the hot water heater inspected the element and thermostat refilled and it puts out hot water (intermittently).

I am not aware of an accumulator tank (though it could be hidden behind a bulk head).

My thoughts turn to an issue with a check valve that may have gone bad.

R
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Old 02-01-2016, 16:50   #4
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Re: Hot Spigot produces cold, then hot, then cold etc.

What kind of hot water heater?

Some have mixing valves for example that can go bad and cause similar symptoms.
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Old 02-01-2016, 17:53   #5
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Re: Hot Spigot produces cold, then hot, then cold etc.

The hot water heater is a Raritan 1700. Thermostat and heating element checked out. For what its worth the water is also heated from the engine when it's in operation.

I've not tested for this hot / cold / hot / cold phenomenon when under way though.

The URL below is the pdf of the owners manual.

Thanks!

Rick

http://raritaneng.com/pdf_files/wate.../L206v0911.pdf
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Old 03-01-2016, 06:45   #6
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Re: Hot Spigot produces cold, then hot, then cold etc.

Quote:
Originally Posted by rwells36 View Post
The hot water heater is a Raritan 1700. Thermostat and heating element checked out. For what its worth the water is also heated from the engine when it's in operation.

I've not tested for this hot / cold / hot / cold phenomenon when under way though.

The URL below is the pdf of the owners manual.

Thanks!

Rick

http://raritaneng.com/pdf_files/wate.../L206v0911.pdf
Doesn't appear this unit has a mixing valve and Ive not noticed one on other Raritans. Some Isotherm units have them.

Could be a plumbing issue: leak between hot/cold side at the mixing fixture. Does it just happen on one fixture?
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Old 03-01-2016, 06:52   #7
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Re: Hot Spigot produces cold, then hot, then cold etc.

Quote:
Originally Posted by belizesailor View Post

Could be a plumbing issue: leak between hot/cold side at the mixing fixture. Does it just happen on one fixture?
+1
The check valve will mitigate this but it is not the root cause. The leak will be increased if there is pressure drop in the hot side.


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Old 03-01-2016, 09:47   #8
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Re: Hot Spigot produces cold, then hot, then cold etc.

all fixtures have the same issue.

R
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Old 03-01-2016, 09:49   #9
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Re: Hot Spigot produces cold, then hot, then cold etc.

It appears the water going into the water heater is under pressure, but if that pressure wasn't maintained it seems logical that the hot and cold would mix in and out. I have noticed that the hot turns to cold when the pump kicks in. Pump runs for a minute, kicks off and the hot water returns.
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Old 03-01-2016, 11:43   #10
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Re: Hot Spigot produces cold, then hot, then cold etc.

Here's a fresh water schema...
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Old 03-01-2016, 15:16   #11
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Re: Hot Spigot produces cold, then hot, then cold etc.

There is air trapped inside your hot water tank. When the water is heated, the air expands, pressurizing your water system and forcing water out of the hot water tank back into the cold supply line. The pump also pressurizes the system, forcing water in the opposite direction. Depending upon which source of pressure is greater at the moment, you will get either hot or cold water flowing from your faucets. Turning on the hot water briefly, in order to release the pressure in the hot water tank, will usually fix the problem - until the next time your hot water is heated.
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Old 03-01-2016, 16:22   #12
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Re: Hot Spigot produces cold, then hot, then cold etc.

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Originally Posted by fguptill View Post
There is air trapped inside your hot water tank. When the water is heated, the air expands, pressurizing your water system and forcing water out of the hot water tank back into the cold supply line. The pump also pressurizes the system, forcing water in the opposite direction. Depending upon which source of pressure is greater at the moment, you will get either hot or cold water flowing from your faucets. Turning on the hot water briefly, in order to release the pressure in the hot water tank, will usually fix the problem - until the next time your hot water is heated.
If the tank is installed correctly (outlet draws from a high point) the air will go out when you open the hot water faucet. If the tank is installed incorrectly (outlet draws far from the high point) then the air above teh outlet will remain in there creating havoc.
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Old 03-01-2016, 17:23   #13
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Re: Hot Spigot produces cold, then hot, then cold etc.

Is there a check valve installed in the system?

Most manufacturers recomend them, but I rarely see them installed.
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Old 04-01-2016, 13:37   #14
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Re: Hot Spigot produces cold, then hot, then cold etc.

We have a problem that we think is the fresh water pump.


There is no water pressure, and the tank is full.


We turn the pump off open the valve, then turn on the pump and it runs and there's water pressure.


Tried it again today, but it didn't work. We think we need a new water pump. Any ideas?
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Old 04-01-2016, 14:56   #15
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Re: Hot Spigot produces cold, then hot, then cold etc.

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Originally Posted by Steve1944 View Post
We have a problem that we think is the fresh water pump.


There is no water pressure, and the tank is full.


We turn the pump off open the valve, then turn on the pump and it runs and there's water pressure.


Tried it again today, but it didn't work. We think we need a new water pump. Any ideas?
Yup, seperate thread.
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