Hot water flow diminishing

Wedgie

.
Jul 30, 2013
23
Hunter 45cc Rosslyn Bay Qld Australia
We own a Hunter 45CC and the flow to the hot water taps in the heads and galley have been slowly becoming less and less until it is now down to a trickle..
We have checked the pump filters which had very little debris at all and the pump doesn't seem to have any issues either as the cold water flow is unaffected.
Our thoughts are that there may be some calcification in the hot water lines or tank (which is under the bed in the aft cabin) and wonder if anyone else has experienced this problem and how they addressed it.
We would be appreciative of any suggestions.
 
Apr 11, 2010
946
Hunter 38 Whitehall MI
There is likely a mixer valve on the water heater right where the hot line exits. It's designed to mix the hot with a flow of cold as a way to moderate the temperature and lower hot water consumption as a way to stretch the supply.

It is brass and has a multi sided plastic knob on top with a screw in the middle. You will see arrows that point to making it hot or cold by bleeding in more or less cold.

There are screens with fairly small holes on the inlet and outlet sides. These tend to easily scale up. I found some fibers from when the boat was plumbed at the factory.

I ordered a replacement. It wasn't to bad to install. I did find in the course of replacing it that I likely could have cleaned it.

There are threads on this so if you search the archives you should find them. If I can locate it, I'll update this response with the links

I found the thread

https://forums.sailboatowners.com/index.php?threads/low-hot-water-pressure.157788/
In this thread there is a link to the manufacturer of the product. Also a schematic
 
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Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
I have had hot water side of my sink faucet and the head shower calcify slightly, plugging the valve on that side.. usually though it plugs the aerator screen which affects both hot and cold..
Look for a mixing valve, later model boats had them from factory.
 

Wedgie

.
Jul 30, 2013
23
Hunter 45cc Rosslyn Bay Qld Australia
Thanks Quadrille38 but couldn't find the link to manufacturer or schematic anywhere. Can you point me in the right direction?
 
Dec 19, 2006
5,809
Hunter 36 Punta Gorda
Had the same thing happen on my H-36 2007 and it was at the hot water heater where the hoses
Are connected to the water heater and there are screens that were all clogged and just disconnect the hot water hose coming out of the heater and cleaned the screens and been working great ever since.
Try the screens and did not do anything the the mixer
Nick
 
May 10, 2004
113
Hunter 340 Bremerton, WA up from Woodland
Another thing to try... We had a factory installed "cheap" plastic check valve at the HW Heater cold water inlet that disintegrated. Replaced with brass - full flow restored.
 
Oct 19, 2006
337
Hunter 27-3 Brownsville, VT/Mystic, CT
I vote for the screen on the hose coming out of the heater and into the mixer. I was just fighting with that same problem last weekend on my '07 H27-3. We had nothing at all coming out of the hot side. It's been on my to-do list for this new-to-us boat all season, but there were 50+ other items higher up than that!

After I got it flowing, I had the dreaded rotten-egg smell, so had to shock the system. While flushing through, the hot flow started to slow again. Opened it up and, lo and behold, more crap clogging the screen. I anticipate I may have several bites at this apple...

My understanding is the mixer more of a scald-preventer when the engine is heating the water. Some folks have eliminated the mixer entirely because of this clogging problem and just are careful to be sure they don't scald themselves by opening cold first at the tap.
 
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