Help with water pressure

[doctorbill]

On my Hunter 420, a while back I found that the factory installed 11 gal Seaward water heater was leaking. Some basic searching lead me to find that these aluminum heaters frequently leak, so in replacing I went with a Torrid 10 gal stainless steel vertical orientation tank (also looked at Isotemp brand but limitations to my install space made the Torrid a better fit). Anyway, besides the leaking heater, I always had good water pressure from the city supply dockside hookup prior to changing the heater...

So, after install, no leaks, but water pressure from the dockside freshwater hookup is reduced whenever I first open a faucet either cold or hot after not having used water in a while. Let's say I have not used water in 4 hours... I open a faucet and initially there is sort of a "blast" of good water pressure, then it quickly goes down to just a dribble, and then over about 60 seconds comes up to around 60% of what the water pump will give. Everything works fine as expected when I use the water tanks and the water pump (both cold and hot), but I live aboard so really like the city supply option (which worked fine before I changed the heater). I tried changing out the thermostatic mixing valve because the water was also not hot enough (even though water from the T&P relief valve was super hot). After changing the thermostatic mixing valve everything seamed better for a day, and water was hot again, but then the pressure problem. I get what seems like normal pressure from my hose prior to the boat hookup and I even tried removing the pressure regulator I had installed at the city faucet.

Please help! I stay up nights trying to figure this!!!

 

[Rick D]

Sure sounds like the mixing valve. I would send a PM to Main Sail since he used to be a distributor for water heaters in another life as I recall.

 

[Bill Roosa]

well the mixing valve does not even enter into the circuit on the cold water side so you can probably rule that out.
since everything works OK when on the ship's water pump the problem has to be:
low city water pressure (unlikly since it does have good pressure once it sits for a while)
pressure regulator (you said you checked that)
a kink in the water hose???
an obstruction in the line between the pressure regulator and the check valve on the ship's water pump

 

[Tom J]

Sounds like a restriction at the city water hookup. Is there a screen at the hookup that would catch debris from the hose? I use a filter on my hose when I fill my fresh water tank, and you wouldn't believe the stuff that comes out of that filter when I back flush it. The water in the dockside plumbing sits in the pipes for days at a time, and things tend to grow in there.

 

[Rick D]

Oops...

well the mixing valve does not even enter into the circuit on the cold water side so you can probably rule that out.

Well, dang. I just sorta assumed that if it mixes, it did so by mixing hot & cold. Guess I better shut my mouth and do some reading... Sorry.

 

[woodster]

did he by any chance change the incoming water supply fitting in any way that could have something to do with ...like putting the water to the hot water heater first the feeding the rest of the system after the water heater....just some thoughts here dont know if it would make a dif or not ......

regards

woody

 

[Ron20324]

Where is the city water connected into the ship plumbing? There was a thread a few weeks ago about using city water in a boat's plumbing system. And, don't believe everything you read. There IS cold water in the "MIXING" valve. Otherwise, how would it "MIX" to cool the hot water?

 

[Fred Villiard]

My first thought wwould be that you kinked or pinched the city water supply line while replacing the water heater.

 

[doctorbill]

So I agree with all the logic here. I am now looking further upstream from the water heater, as clearly the system works fine with the pump.

The cold supply to the faucets is direct and prior the the water heater's thermostatic mixing valve. The idea of a mixing valve is to mix the 140 degree hot water coming off the water heater with a supply of cold water so that all of the hot water pipes in the boat receive "warm" 120 degree water, so that two supplies go to each faucet - a pure cold and a mixed "warm." And thus, I had concluded that the mixing valve could not be responsible for my restriction... but I replaced it anyway, so I have now eliminated that issue.

I started poking around last night at the dockside hookup to the stern of the boat. I realized that a full inspection and cleaning will take a while, so I just hooked it back up, and... Seems to be working much better. Maybe just jiggling it around relieved an obstruction?

Like I said, I am going to fully inspect the pressure regulator at the stern where the hose connects as my next culprit to go after. The hose is not kinked and flow is good when I just spray the hose into the marina, so it seems to be at the boat level, prior to the water pump and water heater.

Thanks for helping me brainstorm this.