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Hot water coming through cold lines

Jan 22, 2008
20
Catalina 310 77 Atlantic Highlands NJ NJ
Just back from a trip to Long Island Sound, mostly motoring, but the thought of a nice shower at the end of the day was hampered by the hot water being unsafely hot and the cold water spigots putting out hot and cold water intermittently. Letting the cold water run helped, but there is limited water on board. I am thinking that cold water lines are touching the hot? Does anyone have any experience with this.

Thank
Jack
 

jviss

.
Feb 5, 2004
4,580
Tartan 3800 Westport, MA
My guess is that there's no check valve at the input to the water heater, and the hot is backing up into the cold lines. Also, guess you don't have a tempering valve on the heater output.
 
Jan 22, 2008
7,647
Beneteau 323 Annapolis MD
Sounds like the heater is stuck "on" and the excess water pressure developed is pushing back out the cold input or just conducting it via the pipes.. Bad Thermostat? I agree, a tempering valve is a great idea. Sunday morning on the hook, the water is hotter and there is more of it.
 
Jul 23, 2009
367
Beneteau 31 Oceanis Grand Lake, Oklahoma
My boat does the same thing. I think its a combination of no/bad check valve and the fluctuating water pressure in the system. It's one of the items on the long list of things to fix.
 
Mar 30, 2007
64
Catalina 310 Manalapan, NJ
Hi
I had a very similar problem. It was due to the aerator being clogged with debris and causing back pressure. Check it our because it is an easy fix
Jeff
 
Jul 23, 2009
367
Beneteau 31 Oceanis Grand Lake, Oklahoma
Hi
I had a very similar problem. It was due to the aerator being clogged with debris and causing back pressure. Check it our because it is an easy fix
Jeff
In the last two weeks I've had to clear aerators in my home and my RV. I'll check it out.
 
Jan 22, 2008
20
Catalina 310 77 Atlantic Highlands NJ NJ
As of now I'm not sure if there is a check valve. I looked at the Catalina 310 Manual, and there is supposed to be one there. The one Catalina sells fits a 1/2 inch hose. I will look for that when I get to the boat. Chances are it failed, so I will remove, check and replace if necessary. Not sure what a tempering valve is. Is it like a "mixing Valve?" When you say Thermostat, do you mean the one on the engine or is there one inside the heater? Where is the aerator? Is that in or near the pressure tank? I admit to being a lot lost here. I appreciate your help.
Thanks Jack
 

jviss

.
Feb 5, 2004
4,580
Tartan 3800 Westport, MA
Not sure what a tempering valve is. Is it like a "mixing Valve?"
Yes, it is. It has three ports, hot in, cold in and mixed out. There's a way to adjust it, too.

Here's mine:



Unfortunately it's in Celsius, but I've never see none of this type in Fahrenheit.

The trick is finding one that will work at the low rates of flow we see in boats.

(I haven't installed mine yet.)
 
Jan 22, 2008
7,647
Beneteau 323 Annapolis MD
Yes, it is. It has three ports, hot in, cold in and mixed out. There's a way to adjust it, too.

Here's mine:



Unfortunately it's in Celsius, but I've never see none of this type in Fahrenheit.

The trick is finding one that will work at the low rates of flow we see in boats.

(I haven't installed mine yet.)
That valve looks just like the one I got online. I have it on 38, which is 100.4 on my chart, and I can use it as-is- without cold water added in. The hotter settings are too hot for skin/hands. On 38, the first couple seconds are a little hotter, so either make a cup of tea with it, or wait a couple seconds till the 38 comes out. It is one of the best upgrades I made.
 
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Likes: jviss

KZW

.
May 17, 2014
711
Catalina 310 #307 Bluewater Bay, FL
That valve looks just like the one I got online. I have it on 38, which is 100.4 on my chart, and I can use it as-is- without cold water added in. The hotter settings are too hot for skin/hands. On 38, the first couple seconds are a little hotter, so either make a cup of tea with it, or wait a couple seconds till the 38 comes out. It is one of the best upgrades I made.
Where is it located in the water line? Do you have a picture?
Do you have a source / part number?
 
Feb 8, 2014
1,197
Columbia 36 Muskegon
Check valve is on the cold input to the heater and prevents hot water traveling back up the cold line as the pressure increases. And with 180 deg coolant heating the water, it increases a lot. Aerators are the removable screens on the faucets. Don't think they're the problem here, I'd bet on the check valve failed / never there in the first place. The water heater in your house has one, it's code everywhere. Mixing or tempering valve connects the cold in and hot out at the heater, adds cold to the hot to get a safe temperature. Also code in a lot of places for the heater in your house, but more important on a boat because of the high temps involved. The thermostat on your house water heater probably won't even go as high as your engine temp will.
 
Jan 22, 2008
7,647
Beneteau 323 Annapolis MD
I had the link right to the vavle via the Watts.com web but the valve and alot of other stuff is now discontinued. Looks like they have gone to bigger business supplying? You can probably google tempering valves and find other sources. You local plumbing supplu might have them. I located the valve under the head sink, as that is where the water tee'd off to go to the galley and made the job alot easier. JGw WAS SPOT ON ABOUT THE PROCESS.
 

jviss

.
Feb 5, 2004
4,580
Tartan 3800 Westport, MA
I got mine on eBay. There are tons of them available, inexpensively.
 
Nov 16, 2012
921
Catalina 310, 2000, #31 Santa Cruz
Here's a picture of how I did mine, on a C310. The tempering valve is on the hot outlet. There's stainless braided tubing from a tee in the cold inlet line. Hidden behind the black/blue NEMA 2K connector is the check valve. Valve is from Amazon: https://smile.amazon.com/gp/product/B00SYC1IV6

IMG_0082_small.jpg
 
Jan 22, 2008
7,647
Beneteau 323 Annapolis MD
While looking for the information for another thread for a cutlass bearing, I found the box the valve came in.

3-way Thermostatic Mixing Valve KESHILI Sanitary Ware Ltd.
KES ML100 made in China, Bar code X000Q916PT