Presure relief valve

[Mikenda]

The pressure relief valve on my calorifier has started to release water randomly, even when the water is cold i.e. on returning to the boat after 24 hrs the pump will run for a few seconds filling up the overflow container. Any ideas please?

 

[boatmike]

Yes! Replace it. I just replaced mine for the same reason. The seating had corroded. New ones available from ASAP supplies mail order.

 

[Roberto]

thanks boatmike!
I have the same problem, I do not know if the leak is in the cold or hot water system but indeed the pump runs for a few seconds every 10minutes or so
I checked all the piping but haven't found any leak: where are the pressure relief valves usually seated ? are they separate from the tank or usually on the tank itself ?

 

[Skysail]

The PRV is usually on the calorifier tank. Easy to replace but sometimes difficult to get at - we had to remove the tank.

Lots of info on this on the Moody Owners website including a current thread.

The problem can sometimes be due to sediment being trapped in the valve. It then clears itself but recurs.

 

[boatmike]

It depends on the type of calorifier you have but its somewhere on the tank itself usually. There are 2 pressure settings usually found. 2 bar and 3 bar. There was a batch of 2 bar valves that had an insufficient free movement on the seating so that marginal wear caused leakage. The 3 bar ones are usually OK. I have replaced mine with a 3 bar one as any calorifier ought to be OK at 45psi. and all my hoses and connections have been pressure tested to 60 psi anyway. The reason for the valve is to release pressure built up when you heat the water, but I think it would normally not be a problem to fit a 3 bar one to most systems. ASAP have both however.... You need to check the thread on the old one. It is probably 1/2" BSP male stud on the tank with a female thread in the valve. If so the ASAP part no is 518772 for 2 bar and 518773 for 3 bar. If its 3/4 BSP they can order them for you as specials or supply thread adaptors for anything else.

 

[Roberto]

thanks a lot

as the calorifer is enclosed behind a bulkhead I have just a little opening to check it, will have to trust my hands..

thanks mike

 

[boatmike]

Bloody boatbuilders often do that! Calorifiers get built in to inaccessable corners. One advantage of building your own boat.... Don't forget to drain down the tank before removing it....... One other thought. I did one on a similar French boat for a guy where it was absolutely bloody impossible to get at but the pipe from it was accessable. We just put another 3 bar valve on the end of the pipe.... Not a good solution but it worked OK!

 

[Plan_B]

I had a similar problem on my Moody, but only when the water got hot (no expansion vessel) Having replaced the PRV and reduced the water pump pressure it still let by when hot. So when I was satisfied that the PRV was doing what it should do, I tee'd a pipe from the PRV into the cockpit drain and have never had water leaking in the boat/or container since and I'm not loosing any pressure in the system.

I've now got another boat with a new calorifier, and it lets by .........

Regards

Dave D

 

[Robin]

Roberto

On our Sun Legende the calorifier has easy access also from the aft port side cockpit locker where there is a removeable panel. Our release valve leaks when added pressure is put into the system from the tank heating up, ie the system is already pressurised by the pump then when we run the engine the water heats up and increases the pressure still more and the valve opens to relieve it. In our case once this happens the valve holds the pressure OK, so our solution was extremely simple - the outlet tube from the relief valve used to go into the bilge, it was long enough already to loop over the bulhead into the gas bottle locker which drains overboard! This was a temporary measure when we first bought the boat and it is still on the to do list to put an overboard skin fitting up under the toerail by the water tank overflow fittings.

Robin

 

[Roberto]

thanks Robin,

I did not check properly but at first sight I had the impression that the panel on the cockpit locker was fibreglassed to the hull and cockpit moulding, but I will check more accurately as it may only be a thin layer of paint/gelcoat over simple sealant

thank you
r

 

[boatmike]

Indeed Robin and Plan_b. Thats exactly what it's supposed to do so the end of the pipe needs to go to drain somewhere. Personally I drain mine to the engine room bilge which has an automatic bilge pump installed anyway but you should only get a small amount of water out of it as the calorifier heats up, not a continuous flow from the pressure pump.

 

[Robin]

I measured the amount by the very scientific method of putting the overflow tube in an old tonic bottle! The amount each time was not very much, maybe a cupful, but it would happen every time the engine was started or the immersion turned on and over a holiday it was quite a bit of water. In our case it found it's way to the engine bilge which is shallow and flat and although there is an auto pump in there it never works as the water escapes on heeling to other areas before there is enough to cover the suction pickup and for the pump to work. I like to see dust in the bilges, water is supposed to be outside if salt and in the tanks if fresh!

 

[Robin]

Roberto

Maybe yours is different or ours was modified before we bought it because our locker has a cut out covered by a simple plywood panel just held in place by a line/cleat, it is probably big enough to take the calorifier tank out through into the locker. It would be easy to make a hole with a jig saw and a ply panel to cover it, this would also allow access to the immersion heater element.

Robin

 

[Roberto]

I ll have a more careful look next time,

actually, the leaks from the valve+pipe are quite minimal, I am more bothered by the the pump going on and off every 10minutes in the middle of the night (until I switch it off) -.<)

 

[boatmike]

Good reason to route it elsewhere then! For the record my catamaran has the engine mounted in a dedicated central compartment seperate from the hulls themselves which is easily cleared by a bilge pump. I do have dust in the bilges in the hulls!
For those who want to do so don't forget that the exit from the pressure valve can flow "uphill" to a skin fitting should you so choose....