Hot Water Tank

[stretch33]

My hot water tank always squirts a bit of water out of the pressure relief valve, now it does this when either the hot water is off or on and if l open the cold tap with no hot water in the tank...Its got no leaks and work fine from both mains electric and engine.... Any one got any idea's Ta in advance

 

[Shakey]

Do you know if your HW tank contains some sort of diapraghm that is pressurised on one side to help maintain the water pressure and/or to reduce water hammer?

 

[stretch33]

Hi Shakey, Not as far as l know, when l had it all out it looked like an empty cylinder with the coil inside is all. Its an upright version by the way...any more thoughts most welcome

 

[Shakey]

Perhaps a fault with the pressure relief valve?

 

[Plan_B]

Had a similar problem with my calorifier but only a teaspoonful every few days. I vented the PRV 2 -3 times into a dish and that seemed to help - probably a bit of grit on the seat. In the end I piped the PRV into the bilge and it seems to just evaporate.

If it just happened when the immersion/engine heat exchanger was on, then I would think it would be down to expansion in which case (I am told) a small accumalator might help.

DD

 

[nedmin]

If you didnt get some water out of the pressure relief valve it would burst the tank. The pressure relief valve is only doing its job and it is quite normal. When you heat water up it expands.my output pipe from the calorifier pressure relief valve goes out of the engine vents,to go outside.

 

[peteandthira]

I have fitted a NRV in the feed to my hot water tank, with one of those expansion tank doodahs in the line downstream from the NRV.

This stops any undesirable hot water activity and only results in a small spurt (!!) when one opens the HW tap, just before the pump starts. I think that means that the expansion tank is now empty again and awaiting more hot water excess pressure.

We also have one of those new-fangled Jabsco variable pumps, which required the above set-up, and can recommend them for low noise and low power.

Pops

 

[TrueBlue]

I had the same problem, the final solution was to have a pressure valve set to a tad more than the pressure switch on the pump (I fitted a 3bar tank with valve and the pump only does 2.5bar).
A temporary solution is to turn the knob on the top of the valve - it has a cam like action which I suppose it intended to clear off any calcification.

It usually happened when re-establishing pressure from "off". I always release pressure when leaving the boat. As other have done I run a pipe from the overflow boss into the part of the bilge that gets pumped.

 

[marcusgillies]

OK here we go.
firstly remove all non return valves, The amount of water returning to the cold side from expasion in not noticable. Then pipe the accumulator tank on to the HOT side of the system (idealy you need an 8 litre one) or add another to this side somewhere close to the calorifier.
Check the pressure of the water pump and the accumulator tank the latter should be a few psi below the cut out pressure of the pump.
If your problem only ocours when the calorifier is heated by the engine cooling, Cleghorn Waring make a rather nifty little valve (CW276) which you plum into the pressure side pipe feeding hot engine water to the calorifier. this has a sensor you fix to the wall of the calorifier. when the water in the tank reaches the desired temp it cuts of the coolant circulation to the calorifer.
The majority of calorifiers and home immersion heaters run at 55-60C your engine prob runs at 82.
However if your engine is a Nanni Diesel you will need the 3 way model of that valve as cutting of the circulation on this make of engine will cause overheating.
hope this helps