Leaking pressure relief valve

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Jegs

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Help,

I replaced a leaking prv with a new one & still have the same problem.

The pump is rated at 2.5 bar, the valve 3.0 & the accumulator [if relevant] max 8.5.
The top of the accumulator is above the main tank but below the top of the hot water tank: with the pump switched off I released the valve on top of the accum. with a small fountain being the result. I thought that these things had a membrane inside which would have prevent such a gush, am I wrong again?

Might a build up of calcium in the hot tank cause the problem?


Mystified & hopeful,

John G
 
I have no direct knowledge of a boats accumulator but I thought it was like a pressure vessel on a central heating system if so it should have a shraeder valve on top to top up occasionally the air/nitrogen side. If water comes out of this valve when it is pressed the diaphragm is knackered, If it is, when every thing heats up the expansion of the water will have no where to go and will leak off through the prv.
Pete
 
pete said:
I have no direct knowledge of a boats accumulator but I thought it was like a pressure vessel on a central heating system if so it should have a shraeder valve on top to top up occasionally the air/nitrogen side. If water comes out of this valve when it is pressed the diaphragm is knackered, If it is, when every thing heats up the expansion of the water will have no where to go and will leak off through the prv.
Pete
Click to expand...

Yup, wot 'e sed!
 
Don't some accumulators have air on one side of a diaphram and the pressurised water on the other? Sometimes the air needs topping up (with a bike pump on the valve) so that the pressurised water has some to compress as it expands. Failing that it doesn't work as an accumulator. This doesn't account for the fountain but prvs do leak don't they - I thought that was what they did and why many folks put a hose on them overboard (on the transom say) or a bottle that can be emptied (rather than it going in the bilges).
 
Accumulators

Some accumulators have a "rubber" bag in them. Some don't, and are just a chamber, initially filled with air, which is compressed by the pump. You need to find out what type of accumulator you have.
 
Its probably doing its job.As water heats it expands this will open the prv.its quite normal,mine does it all the time.You need to vent overboard.Mine goes out the engine breather vent.
 
Jegs said:
Help,

I replaced a leaking prv with a new one & still have the same problem.

The pump is rated at 2.5 bar, the valve 3.0 & the accumulator [if relevant] max 8.5.
The top of the accumulator is above the main tank but below the top of the hot water tank: with the pump switched off I released the valve on top of the accum. with a small fountain being the result. I thought that these things had a membrane inside which would have prevent such a gush, am I wrong again?

Might a build up of calcium in the hot tank cause the problem?


Mystified & hopeful,

John G
Click to expand...

It sounds as though your accumulator has no air in it, whether a non-diaphragm type, or if it has a diaphragm this is broken and there is no air in it, assuming it to be mounted upright. Normally an accumulator will absorb the expansion of a calorifier, so that the prv does not blow.

I suggest you get the accumulator sorted first, then see what happens at the calorifier.
 
Most accumulators have a rubber bladder inside a pressurised cylinder.

The pressure in the steel outer chamber is at between 1.2-1.8 bar.
It sounds as if your accumulator bladder has ruptured.

The most effective cure is to replace the accumulator in toto.

Many calorifiers have a one-way valve to prevent back siphonage into the main system.

An alternative is that the air pressure in the accumulator is too high, but that is very unlikely unless you've topped it up through the Schrader valve on top.
 
My Jabsco accumulator does not have a diaphragm and needs to be vented occasionally. I changed to this after the failure of several diaphragms.
 
In my experience when you switch the calorifier on the water heats and expands and the prv releases some water. If you leave the calorifier on it doesn't leak more. Thus the leak seems normal unless it leaks all the time.
 
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