Plumbing problem - pressure relief valve?

TerryMac

TerryMac

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Hi,

I am having a problem with my plumbing and was hoping someone could assist me.

I have a C-Warm water storage heater that runs as a calorifier and an emmersion heater (when plugged in shoreside). There is a temperature / pressure relief valve fitted so that when the water heats up the excess is drained off. This is fitted so that the excess water flows into the shower sump. Sometimes when I am motoring for a long period of time I notice some water in there and pump it out. Quite often if I am motoring I will switch the water pressure switch off and this stops water collecting there.

The other day I noticed that there was a lot of water in the shower sump, we had been motoring for quite a while so I wasn't too alrmed. I pumped it out. However, over the past few days the problem has got worse. As soon as I switch the water pressure on a spurt of water continously flows into the shower sump (regardless if I have the engine on). This happens if I let the water cool so I doubt it is a temperature related problem. This leads me to belive that the pressure relief valve has gone.

I am going to block the outlet of the pressure relief valve and switch on the water pressure. When it gets up to pressure (2 bar) I should hopefully hear the pump cut out. This will prove the pump switch.

After that I intend to drain off the storage heater and inspect the pressure relief valve. Does anyone know how I can test this?

The storage heater is a C-Warm model. I believe the correct replacement is CW414 Temperature Pressure Relief Valve 2.5 Bar. Is this a standard size and will I be able to get one from a plumbing shop? I am currently in NW Spain (Portosin), does anyone know of any dealers / suppliers in this area?

Any assistance / advice would be greatly appreicated.

Terry
 
The instructions with my calorifier say that the PRV is essential and that you should ensure that it is working by turning the knob on it from time to time so that you can see it dribble. If you have stopped it from working whilst motoring then perhaps the pressure has popped off one of the connections in your plumbing. Is the water going into the shower pump hot (from the PRV) or cold (from earlier in the system)?

In a Moody the PRV dribbles into the bilges and 2 solutions are either a bottle on the end of it which can be emptied now and again or a hose from the PRV that goes overboard at a suitable point (on mine that is the transom).

I imagine the PRV to be a standard item but I have never been into a plumbers looking for one.
 
You MUST have one and yours is clearly faulty. Turning off pump is an acceptable solution, blocking the valve is not! You can get one here http://www.cleghorn.co.uk/c-warm-heaters...valve-25bar.htm or the plumbing equivalent here http://www.advantay.co.uk/cat001.asp also 2.5 bar. You should also be able to get them easily in Spain as well, I don't speak the language but look here http://www.b2b-europe.com/main.php/langu...umbing+Supplies as a start. 2.5bar with a 1/2" thread and the metric continental equivalent should be readily obtainable anywhere. Metric threads are the same as ours in spite of us calling ours 1/2" or 3/4". Sorry can't be more helpful.
 
MoodySabre - Thanks for the reply.
I don't stop it from working when motoring - I just switch the water pressure switch off so that the water system is not pressurised.
The water coming out into the shower sump is warm, I can actually see it coming out of a clear tube that is connected to the PRV so I am confident that it is coming out of the PRV and not from anywhere else.
I have tried twisting the knob on the PRV but nothing seems to happen.
 
I recently bought and fitted a new one. It's not something that seems to be available in every plumbing supply shop, it is heating engineer establishments that tend to stock them, at least around here it is.
Cost about 11 quid. If twiddling the knob on the existing one doesn't cure the problem, I would simply change it if I were you, it will only get worse! /forums/images/graemlins/grin.gif
Get a proper look at it before going to look for the replacement, they vary as to male/female connections.
 
Thanks for the advice.
I have blocked the tube that exits from the PRV and run the water pressure switch. The water pressure switch cuts out (as it should) so this proves the switch.
I guess it must be the PRV. How do they work? Can I fix it or test it?
 
[ QUOTE ]
......I guess it must be the PRV. How do they work? Can I fix it or test it?

[/ QUOTE ]
No! See my post above. /forums/images/graemlins/shocked.gif
 
As others have already said, and as you obviously suspected, you need a new PRV. Make sure it's the same value as the existing one.

The reason the PRV (even when working correctly) allows a little water to escape when the calorifier heats up is that the water in the calorifier expands and builds up pressure. If you ever want to eliminate this behaviour (doing which will extend the life of the PRV and also save the water draining into the shower sump) then you could fit an accumulator in the output circuit from the calorifier. This would absorb the expansion and keep the pressure below the PRV value.
 
PRVs are quite crude; basically a spring loaded plunger presses a cone against a similarly shaped face in the body of the valve.

These get calcified in time - causing a leak.

If you can dismantle the unit - then do so and clean the faces of the cone/ valve with steel wool / kitchen pad or whatever.

Some valves actually turn the cone part when you twiddle the top - to help clean the two faces.

Both methods above might work as a jury rig!
 
[ QUOTE ]
[ QUOTE ]
......I guess it must be the PRV. How do they work? Can I fix it or test it?

[/ QUOTE ]
No! See my post above. /forums/images/graemlins/shocked.gif

[/ QUOTE ]

As said. Some PRVs can be dismantled(carefully). Its often just some scale or a bit of grit caught in the seating. You can clean the seating, but be careful as some use a rubber diaphragm onto the seating and you must not damage/rip that.

As long as you are careful its quite in order to overhaul a PRV in this way, but if you are in distant parts what I would do is source a replacement and fit that, then see if you can service the old one and keep that as a spare. If you knacker it trying to service it without a spare you are a bit stuck.

We clean and service dripping PRVs on pressurised heating systems every week. We replace some as well of course, depending on condition.

Tim
 
[ QUOTE ]
fit a decent sized accumulator so that the relief valve isnt worn out un necessarily

[/ QUOTE ]Yes indeed - but if your system incorporates a non return valve at the cold water input to the calorifier then this will need to be an additional accumulator to any existing one in the cold water circuit, and will need to be installed after the NRV. For instance:
caldiag.jpg
 
I have an accumulator installed after the hot water outlet.

I have received the spare, fitted it and all is OK!

Thanks once again /forums/images/graemlins/smile.gif
 
[ QUOTE ]
Thanks for the advice.
I have blocked the tube that exits from the PRV and run the water pressure switch. The water pressure switch cuts out (as it should) so this proves the switch.


[/ QUOTE ]

No it doesnt . It simply proves that the water pump cuts out but you dont know whether its doing this at the 2 bar it should be or the 3 bar .
 
IMHO on the average boat the PRV is so hard to get at, if it's pretty old it's best to fit a new one and be done with it. On my boat recently it was an hour's work to get at the thing, 5 minutes to change it, and another hour to put everything back. I'd rather cough up the tenner or so and be sure it was going to be OK after all the effort.
 
Point taken and agreed with. You just have to make a judgement on site as to whats best. I'm just an inveterate fixer and like to have a go at keeping things going. I get mad with colleagues who throw new and expensive parts at boilers when sometimes all thats required is a bit of time, thought and adjustment/cleaning.

Tim
 
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