Cold Water Supply

[dino]

For all the issues we can have with boats this is low on the to do list but looking for some thoughts on the cause. I noticed that when I turn any of the sinks on in the boat I get cold water for a few second then it gets warm to hot for a few seconds. if i let it run it will cycle like this entire time with only the cold water side on. Only thing I can think of is that the mixing valve on the hot water heater is back flowing into my cold water supply?
Thanks

 

[Stee6043]

I think the mixing valves are at the faucets, not the hot water tank itself.

I get some of this during the day when the water in my dockside hose gets hot from being outside in the sun. If you let it run for 5 or so minutes does it continue to cycle or will it eventually stop and go full-cold?

 

[dino]

So my hot water tank has a mixing valve on it that connects cold water to the outgoing hot water to adjust the temperature of the hot water supply. At first I thought it was water just getting hot in the lines in the bilge but the cold water when on and running for a while goes from hot to cold consistently......

 

[Skybolt]

So my hot water tank has a mixing valve on it that connects cold water to the outgoing hot water to adjust the temperature of the hot water supply. At first I thought it was water just getting hot in the lines in the bilge but the cold water when on and running for a while goes from hot to cold consistently......

I have never seen that on a boat. Probably installed by the PO. I would remove it and rely on the mixing of the faucets themselves.

 

[boatrboy]

I have never seen that on a boat. Probably installed by the PO. I would remove it and rely on the mixing of the faucets themselves.

I have that too on mine - I’ll find a pic and add it.

 

[Skybolt]

I have that too on mine - I’ll find a pic and add it.

I had no idea, my bad. What's the point, isn't that what the mixer is for? Just another fail point. IMO.

 

[boatrboy]

I had no idea, my bad. What's the point, isn't that what the mixer is for? Just another fail point. IMO.

I posted a pic - I never really paid that much attention to it I since it’s factory.
Dino - I wonder if the check valve (25) is bad allowing hot water in on the cold side??

 

[Stee6043]

Huh, learn something new every day.

I'd replace that braided loop with short stubs of pex that are capped on both ends. See if that fixes your problem. A $25 fix, all-in. What more could we ask for

 

[Creekwood]

I had no idea, my bad. What's the point, isn't that what the mixer is for? Just another fail point. IMO.

Anti-scald for showers I expect. The temperature on most marine water heaters is not adjustable. On mine the temp is definitely able to scald. It would be good to be able to set a mix temp so that its not so hot when running for dish washing and showers. A mixing valve is pretty fail-safe (recognizing that Dino's is failing!) and if I showered on the boat, I would probably install one.

 

[b_arrington]

I had no idea, my bad. What's the point, isn't that what the mixer is for? Just another fail point. IMO.

It’s so you don’t get scalded. You might be able to change the thermostat on the heater to make it colder. But if it’s using the engine coolant to heat the water, that’s going to make it like 160-170 degrees. Safe domestic hot water is like 120. Put your body in 170 degree water and you’re in trouble.

I just replaced the water heater in my boat and had not adjusted the mixing value. After and engine run the water coming out is the tap even set to slight warm from the handle was HOT.

 

[Skybolt]

Anti-scald for showers I expect. The temperature on most marine water heaters is not adjustable. On mine the temp is definitely able to scald. It would be good to be able to set a mix temp so that its not so hot when running for dish washing and showers. A mixing valve is pretty fail-safe (recognizing that Dino's is failing!) and if I showered on the boat, I would probably install one.

I've never used the marina's showers and always used the boat. I have a 15g standard hot water heater that yes, if only hot water on with scald you. Also just like my house, it is free flowing. I use the mixer on the faucet to control the water temp. I have one mixer in my master bath that allows you to change the water temp of the shower. I guess I just don't understand why the regulation on the HW heater is desirable.

 

[Creekwood]

I've never used the marina's showers and always used the boat. I have a 15g standard hot water heater that yes, if only hot water on with scald you. Also just like my house, it is free flowing. I use the mixer on the faucet to control the water temp. I have one mixer in my master bath that allows you to change the water temp of the shower. I guess I just don't understand why the regulation on the HW heater is desirable.

Interesting. I guess when you have a separated shower its less of a PIA to shower on the boat. Our marina showers are nice, clean and close to my slip, and I don't have to clean them. So I use theirs. I think I need to replace my OEM two knob sink faucet with a single lever, which would be more convenient for balancing the temp when washing dishes.

 

[Skybolt]

Interesting. I guess when you have a separated shower its less of a PIA to shower on the boat. Our marina showers are nice, clean and close to my slip, and I don't have to clean them. So I use theirs. I think I need to replace my OEM two knob sink faucet with a single lever, which would be more convenient for balancing the temp when washing dishes.

Yes my shower is separate and has lot's of room. My boat is also a single stateroom boat so it has more room for the comports of home. It's only me and my wife and "dog". The kids never stay on the boat anymore.

 

[dino]

Thanks everyone! Ill replace the check valve. Have a great Season!

 

[dino]

Thanks everyone! Ill replace the check valve. Have a great Season!