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Old 08-17-2019, 02:42 AM   #1
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Hot water from both sides

Aloha again trawler friends. Back again about my water issue. I still haven't been able to fix the foamy water issue. Changed a shutoff valve that I THOUGHT was the problem. Someone had suggested maybe air in the hoses somewhere. Nothing doin'. Drained and flushed the water heater about 10 times now. That WAS/still is the stink water issue. The problem I also have is hot water coming from both sides of the faucets. Kitchen sink, bathroom sink, bathroom shower and outdoor shower. Hot water always. The photo I attached is of the manifold that the dock water comes into after the filter then goes into the boat. My question to you all is, that manifold you see, is there anyway that it is not separating the hot and cold? Do those have a check valve? I've followed all the lines and the only thing I can think of is that manifold, or the water heater is letting hot water back through the cold water inlet. Your help is much appreciated.
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Old 08-17-2019, 07:35 AM   #2
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I have a check valve on the output line of my water heater. Hot is hot, cold is cold, never the twain to meet.

I have a 5 gallon water heater, very inexpensive. It was the source of stinky water. I just replaced it. Pretty easy and cheap. just for fun I cut the old one apart. It was about one third full of a stinky calcium looking grainy residue. No way flushing would have gotten it out.

I have thought of having an engine heat loop in the system but those tanks are expensive. I like the "throw away" 110 volt kind.

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Old 08-17-2019, 08:05 AM   #3
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Question. Are you drawing from your water tank or from the dock?
What is the pressure of your surge tank?
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Old 08-17-2019, 08:20 AM   #4
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[QUOTE=LUVYAPOP;792401]Aloha again trawler friends. Back again about my water issue. I still haven't been able to fix the foamy water issue.

Libya,

Be sure you don't have a leak between the heat exchanger and the potable water. The antifreeze will make the water foamy.. Had that happen in a home system.

Rob
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Old 08-17-2019, 09:10 AM   #5
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I also tend to have hot water from both sides after the engines have run a while. They heat up in the engine room. Both Hot and cold water pipes run right between engines on a stringer uninsulated copper pipes. Copper is a good heat conductor. I need to insulate those pipes with foam tubes, might help it. Where we boat and use fresh water system, warm water is good enough for most things.
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Old 08-17-2019, 09:47 AM   #6
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The problem I also have is hot water coming from both sides of the faucets. Kitchen sink, bathroom sink, bathroom shower and outdoor shower. Hot water always. The photo I attached is of the manifold that the dock water comes into after the filter then goes into the boat. My question to you all is, that manifold you see, is there anyway that it is not separating the hot and cold? Do those have a check valve? I've followed all the lines and the only thing I can think of is that manifold, or the water heater is letting hot water back through the cold water inlet. Your help is much appreciated.

The photo isn't helpful without a diagram of the piping/context. As far as check valves, that would be something that would be installed concurrent with the piping install. There's no "standard" piping there. What you have is what you have. Follow the fittings and diagram it out. That exercise alone will force you to logically step through the piping in order to get it committed to paper, you'll learn about your individual piping layout in the process.



It would be helpful to install check on the cold inlet to the WH. Make sure the direction on the check valve is correct, there should be an arrow or "in/out" legend on the body of the valve, in would be facing the pump outlet. Again, if when the hot from cold condition is present, if the cold inlet is warm, that shouldn't occur.



I recall an older thread that questioned if you have mixing valves, like a shower valve or single lever mixing valve. Particularly with a hand shower valve- if the hand shower has a pushbutton valve that can shut off water flow at the handpiece and the H/C faucet stops are left open, that can certainly cause a bypass condition. A common culprit. They can be elusive to DX, so assume nothing. A kitchen faucet with a pull-out spout and even some single lever faucets can create this condition. Duplicate the action that gives you hot from the cold, then feel the lines at every fixture that has a hot & cold connection with the faucet in its normal closed position; any that has a warm line on the cold (usually left) side would be suspect.
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Old 08-17-2019, 11:41 AM   #7
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Thanks Pete. My water heater has the input and output to add a hose from the heat exchanger if I wanted, but I don't run the boat but once a week and take it out to clean the bottom every three weeks. I was told to run some CLR into it, but guy at Kuuma said NOT to add any chemicals.
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Old 08-17-2019, 11:47 AM   #8
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Thanks Steve. My outdoor shower has a shutoff valve. I also have a shutoff valve for the water coming in from the dock. I made a schematic last night. Going to clean it up so I can post it. Hopefully it will be easier to read. My job in the military was hydraulics, so I understand the flow, just don't know anything about marine water heaters. I'll add a check valve to the hose right before it goes into the cold water inlet. See if that fixes the problem.
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Old 08-17-2019, 11:49 AM   #9
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Thanks Old Dan, I'm running from the dock, but run from the water tank when I'm out to sea. The hoses T at the cold water inlet coming from the dock and water tank. Reason I asked if it could be the water heater failing.
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Old 08-17-2019, 11:56 AM   #10
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Thanks Rob, but the water heater is not connected to the heat exchanger. Independent system. The shutoff valve I had installed in the line coming in from the dock water that goes to the cold water inlet, Ts from the water tank as well. I noticed some air in the hose right after the shutoff valve. I changed it and no more air, but still have foamy water.
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Old 08-17-2019, 12:00 PM   #11
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Thanks SDowney717, but my water system is not connected to the engine, so that can't be the problem. I read what Pete Meisinger said about possibly the water heater being corroded inside. Reason for stink water.
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Old 08-17-2019, 02:18 PM   #12
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Do you have a shower with a shut off at the spray head?
If you do and shut off at the sprayer and not at the temp control valve you can get cross feed of hot to cold piping.
Common occurrence on RVs with an outdoor shower.
Otherwise I agree best to follow and diagram your piping to understand possible causes.
Is this something new? Always been that way? Or boat new to you?
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Old 08-17-2019, 03:10 PM   #13
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As you heat water, it expands and has to go somewhere. Think of the cooling system in your car. When the coolant heats, it expands and goes out the thermostat into the overflow tank. When the engine cools, the coolant contracts and fluid from the overflow tank is sucked back into the radiator.

If there is no air space in your water heater, when the water heats, the expanding liquid has to go somewhere. With no check valves, the water is pushed back into the pressure tank. This would give you hot water out of both the hot and cold faucet. If you put a check valve (one way valve) on the water heater inlet, water is pushed out the safety valve after it's risen to a much higher pressure. This is an extremely poor design.

The best solution is a check valve and then a tee before going into the water heater. Off the other part of the tee you plump an expansion tank. As the name implies, it captures the expanding hot water, preventing it from going back to the pressure tank.

The do nothing approach is to always open the cold water faucet until cold water again starts coming out (usually 2-3 cycles of the water pump).

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Old 08-17-2019, 03:58 PM   #14
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If you shut the hot water heater off and drain the tank, do you still have hot water while feeding from the dock water?
If you shut the hot water heater off and drain the tank, run the engine, do you have hot water out both H/C at the faucets?
I am beginning to think as others. Time to replace the HW heater.
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Old 08-21-2019, 07:16 PM   #15
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I also had to add a check valve to prevent hot water back flow. At the same time, I discovered heat transfer through the engine loop was warming up the front of the engine and wasting electricity. I have installed isolation valves to prevent this.


Daniel
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Old 08-21-2019, 09:24 PM   #16
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I would start by throwing out all that crappy hose, all those c***** clamps and replace it all with Pex and Sharkbite. You will then understand your plumbing much better and never have a leak.

I also don’t like shore water connections like an RV, just fill your tanks and use your own system.
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Old 08-22-2019, 05:24 AM   #17
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I would start by throwing out all that crappy hose, all those c***** clamps and replace it all with Pex and Sharkbite. You will then understand your plumbing much better and never have a leak.

I also donít like shore water connections like an RV, just fill your tanks and use your own system.
Plus 1 on the Pex and Sharkbite. Very easy (fun) to work with and no leaks. Wow!
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Old 08-22-2019, 08:34 AM   #18
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I'll join the crowd recommending a check valve on the water heater cold water inlet.

You can add an expansion/accumulator tank to absorb thermal expansion. No need to go to a "marine" accumulator, it can be an ST-5. Best piping practice locates that tank on the cold water inlet to the water heater, between downstream of the inlet check and the tank connection. That location can be awkward to pipe. A workaround of sorts enables you to locate that expansion tank anywhere in the cold piping with the addition of a tee.

That workaround involves filing a small groove or slot in the seat of the check valve, or drilling a small (< 1/16") hole in the check valve flapper. That provides a small path for thermal expansion to find its way back out of the tank through the check, while retaining the check valve's intended function of preventing flow of heated water into the cold line when a tap on the cold piping is opened.

WRT the OP's backflow condition, the schematic suggests that the cross connection is probably coming from the hand shower. Make sure the faucet valves are closed, and not leaking through. There should be no flow at the handpiece with the valves closed. Put a rubber band around the lever on the hand shower for a couple hours to confirm that the valves are seating. Don't crank them into next week, it'll only serve to damage the faucet washers/stem assembly.
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Old 08-22-2019, 01:41 PM   #19
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I also had to add a check valve to prevent hot water back flow. At the same time, I discovered heat transfer through the engine loop was warming up the front of the engine and wasting electricity. I have installed isolation valves to prevent this.


Daniel

If you'd like to automate the prevention of gravity flow, just add a brass spring check in the line. Use a check with the lightest rated spring available. It will open with the differential provided by the engine water pump, but not from the convection from the hot water in the water heater tank. Once & done & forget it. Make sure you know the direction of flow! Arrow on the check must agree.
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