Banging Pressure relief valve

[Odana]

OK, I'm getting bored of our new boat's plumbing now. non-standard gas pipes, truculent toilet pipes, and now....

 

The 3 bar PRV valve started banging a couple of weeks ago intermittently. Could usually be stopped by turning tap on a bit, then stopping. We have an immersion (left on permanently) on a domestic-sized calorifier which also has an Alde coil (not yet used) and engine calorifier. This got worse, and by weekend was banging constantly, emptying our water into the overflow.

 

We checked pump (Shurflo, 30psi), and the accumulator (2litre unknown make, now set to 20ish psi) - all behaving normally as far as I can see. We took off PRV valve which was full of crud, cleaned it and put back on. Still banging. We ordered a new 3 bar PRV valve and put that on tonight. It leaks from the valve, then bangs. Nowt else from previous threads helps.

 

Now what? What do I check next? I cannot work out what the heck is wrong and why this is continuing. And I want a shower!!! Only thing left I can think of is that this new PRV valve is faulty (it leaks out of top and between red top and brass, not on joints). Before I send it back to Wickes and demand a new one, is there anything else I should be looking for?

 

Yours in frustration....

 

Nicki

[n.b.Goldie]

If the PRV is letting water out of anywhere other than the overflow outlet then it must be faulty.

 

Regards

Ditchdabbler

[Odana]

If the PRV is letting water out of anywhere other than the overflow outlet then it must be faulty.

 

Regards

Ditchdabbler

 

Thought so. Back to Wickes it goes... Mail order only unfortunately. It'll force me to go swimming tomorrow and Thurs so I can have a decent shower. If the new one doesn't work I'll start to lose my temper!!

[wrigglefingers]

If the PRV is letting water out of anywhere other than the overflow outlet then it must be faulty.

 

Regards

Ditchdabbler

 

Agreed, and adding to say I had this problem with Surprise and eventually I solved it by a combination of new valve and reducing the water pressure. It still leaked every so often into a receptable (cut down milk bottle strategically placed and emptied when I remembered). It is bloody frustrating though.

[Odana]

How does one reduce the water pressure on an existing pump? Ours is fixed in an infuriatingly inaccessible hole under front deck, long end facing upwards (ie end with pipe going across down the bottom, near impossible to get to without awkwardly removing pump)

[alan_fincher]

Just to be absolutely certain of one thing.....

 

The accumulator is on a tee off the cold water side of things, (so probably located near the fresh water pump)?

 

Is there any similar kind of vessel plumbed into the hot water side of the system, (which should be acting as an expansion vessel if there were).

 

If there isn't, and there is any kind of non return valve in the feed to the tank, you can reasonably expect some water to be expelled as the tank heats, because it will be expanding, with nowhere else to go. That should cease once it is hot, though.

 

The pump should not however be capable of passing anything through the PRV on its own, because the pump should be cutting out at about two bar, but the PRV not opening unless pressure is 3 bar

 

But whatever else is going down, a PRV should only pass water out of the proper outlet hole. If it is spewing out anywhere else, I think I'd get it replaced by one that doesn't, before investigating anything else.

[wrigglefingers]

How does one reduce the water pressure on an existing pump? Ours is fixed in an infuriatingly inaccessible hole under front deck, long end facing upwards (ie end with pipe going across down the bottom, near impossible to get to without awkwardly removing pump)

 

If I remember correctly, there's a turn-screw or similar on the pump. You apply a screwdriver to it and that does something.

 

Someone with a bigger brain will be along any minute now ....

 

 

Edited to add - I don't know much about pumps but I can replace a broken one in less than five minutes. Must be the number I've broken in the past ....

Edited November 27, 2012 by wrigglefingers

[bizzard]

How does one reduce the water pressure on an existing pump? Ours is fixed in an infuriatingly inaccessible hole under front deck, long end facing upwards (ie end with pipe going across down the bottom, near impossible to get to without awkwardly removing pump)

Is the PRV on top of the calorifier and higher than the hot water outlet?, if not swop them round, they usually use the same threaded bushes.

[Odana]

Just to be absolutely certain of one thing.....

 

The accumulator is on a tee off the cold water side of things, (so probably located near the fresh water pump)? YES

 

Is there any similar kind of vessel plumbed into the hot water side of the system, (which should be acting as an expansion vessel if there were). NO

 

If there isn't, and there is any kind of non return valve in the feed to the tank (CAN'T SEE ANYTHING), you can reasonably expect some water to be expelled as the tank heats, because it will be expanding, with nowhere else to go. That should cease once it is hot, though. ONLY REFILLED TANK W COLD SO FAR - SOON STARTS LEAKING

 

The pump should not however be capable of passing anything through the PRV on its own, because the pump should be cutting out at about two bar, but the PRV not opening unless pressure is 3 bar YEP - GOT THAT - THANKS FOR CLEAR STEP BY STEP SO FAR

 

But whatever else is going down, a PRV should only pass water out of the proper outlet hole. If it is spewing out anywhere else, I think I'd get it replaced by one that doesn't, before investigating anything else.

 

Got it. Ta. New valve it is. Again. And another glass of whisky before bed....

 

bizzard said: Is the PRV on top of the calorifier and higher than the hot water outlet?, if not swop them round, they usually use the same threaded bushes. NOPE, BOTH ON TOP, BUT PRV SLIGHTLY LOWER THAN OUTLET.

 

More whisky. Has been a crappy day and I was hoping for something to go right with a simple valve swap. But ha! This is a boat so it shall never be thus.

 

Thanks all.

[nb Innisfree]

Some pumps have a pressure adjuster on the pump body but it doesn't make much difference and is another place to leak. We have a Parmax 2 running at 26 psi + a 3bar PRV and occasionally have the odd one or two bangs from the PRV which we don' mind as it acts as a sort of regular test but if we had 30psi then I suspect it would be worse.

 

I would say either fit higher pressure PRV or lower pressure pump.

[ditchcrawler]

I would suggest you require an expansion vessel especially considering you have a large calorifier so a large quantity of water expanding.

[wrigglefingers]

See, I told you someone with a bigger brain than me would be round soon. I'm always right 'bout this one.

Edited November 27, 2012 by wrigglefingers

[n.b.Goldie]

I would suggest you require an expansion vessel especially considering you have a large calorifier so a large quantity of water expanding.

 

The OP said they have one, 2 litre set to 20 psi.

 

Regards

Ditchdabbler

 

edited to add; also they have not yet heated the calorifier.

Edited November 27, 2012 by ditchdabbler

[bizzard]

Got it. Ta. New valve it is. Again. And another glass of whisky before bed....

 

bizzard said: Is the PRV on top of the calorifier and higher than the hot water outlet?, if not swop them round, they usually use the same threaded bushes. NOPE, BOTH ON TOP, BUT PRV SLIGHTLY LOWER THAN OUTLET.

 

More whisky. Has been a crappy day and I was hoping for something to go right with a simple valve swap. But ha! This is a boat so it shall never be thus.

 

Thanks all.

I've cured a couple of PRV's that still dribbled from the overflow, in both cases the owner had fitted new PRV's and they still dribbled, they were both on the lower fitting. I swapped them around and it stopped.

Adjusting the pump won't make much difference. On the older Surflow its an Allen screw and on the later Aquaking its a Phillips head screw both on the back centre of the pressure switch. Anti-clock to reduce cut of pressure. I've tried this and it might work for a short period but the problem soon returned.

[n.b.Goldie]

With a calorifier full of cold water not expanding and a pump with a pressure of 30psi why would a 3 bar (43.511 psi) prv let water out the overflow unless it is faulty?

 

Regards

Ditchdabbler

[dmr]

We had all this going on a couple of years ago. Our old pump starting leaking and I replaced it with a notionally identical unit (Sureflo) and then started getting the problem that you describe.

In desperation (and because I'm an engineer) I fitted a pressure guage to work out what was going on.

The pump was producing too much pressure!. The adjustment was fiddly and only solved the problem short term. Also it was very hard to set a low pressure without getting other problems. I thought about fitting an external pressure switch but loads of people kept saying "just get rid of the Sureflo pumo and fit a Jabsco". So I did and now all is well.

Be careful with Sureflo specs, I think the pressure figure is the max allowed intake pressure, not the pressure produced by the pump.

 

............Dave

[Gibbo]

The OP said they have one, 2 litre set to 20 psi.

 

Regards

Ditchdabbler

 

edited to add; also they have not yet heated the calorifier.

 

Are you reading the same thread as me?

 

She said they have a 2 litre accumulator, not an expansion vessel. She said the immersion heater is on permanently.

 

Have I missed something or have you?

[n.b.Goldie]

Are you reading the same thread as me?

 

She said they have a 2 litre accumulator, not an expansion vessel. She said the immersion heater is on permanently.

 

Have I missed something or have you?

 

Is an expansion vessel not the same as an accumulator?

 

In post #9 they said they have only refilled the calorifier with cold water (since fitting the new prv) and it soon starts leaking. Admittedly I am assuming they have not yet turned the immersion heater back on yet.

 

Regards

Ditchdabbler

[bizzard]

I think it can be the initial throb or two from the pump that can hydraulically knock the PRV off its seat i feel it in my water that these initial throbs are of quite high pressure before the pump settles down to below 3o psi.

If the diapham in the regulator is bust then that cushion will be lost, then the pumps sudden hydraulic throb will exacerbate the throbbing hydraulic punches.

By putting the PRV at the top of the calorifier it usually admits a little air which remains under the valve further cushioning the throbs upon the valve until of course when the PRV ever blows off then this little cushion of air will be forced out.

These pumps will easily exceed 43psi or so continuously if the pressure switch has failed and the pump motor is getting a non stop flow of 12v.

Its all about the throbbing pulses from those bloomin pumps.

[alan_fincher]

Is an expansion vessel not the same as an accumulator?

No it isn't the same, nor seeking to achieve the same thing.

 

Otherwise, why would you regularly have both fitted?

[n.b.Goldie]

No it isn't the same, nor seeking to achieve the same thing.

 

Otherwise, why would you regularly have both fitted?

 

I do not know, my previous boat only had a pump, accumulator and 3 bar prv as does my present boat. Neither had any problems.

 

Perhaps you might be kind enough to explain the difference and why both should be fitted, I would be grateful.

 

Regards

Ditchdabbler

[smileypete]

I do not know, my previous boat only had a pump, accumulator and 3 bar prv as does my present boat. Neither had any problems.

 

Perhaps you might be kind enough to explain the difference and why both should be fitted, I would be grateful.

Quick explanation here:

 

http://www.canalworld.net/forums/index.php?showtopic=52306&st=0&p=980017entry980017

 

Possibly your accumulator was doing a bit of both.

 

cheers, Pete.

~smpt~

[n.b.Goldie]

Quick explanation here:

 

http://www.canalworl...17

 

Possibly your accumulator was doing a bit of both.

 

cheers, Pete.

~smpt~

 

Thank you, that was very helpful. My little ship is about 15 years old and the calorifier the same age. As it is working ok at the moment I think I will leave it alone but if any work needs doing I might well fit an expansion vessel.

 

The thread you linked to I think would be very useful to the OP.

 

Regards

Ditchdabbler

[bizzard]

Thank you, that was very helpful. My little ship is about 15 years old and the calorifier the same age. As it is working ok at the moment I think I will leave it alone but if any work needs doing I might well fit an expansion vessel.

 

The thread you linked to I think would be very useful to the OP.

 

Regards

Ditchdabbler

Ahoy DD. Hope you and your landlady are well.

I don't have a calorifier as I have an air cooled engine and Paloma water heater but I work on boats with them and i've found that some boats have neither an expansion vessel nor regulator and they don't seem to have any more PRV blowing off trouble than boats with them, only when the valve becomes old and limescaled up. I think like electrics the more complicated the system the more trouble your likely to give. I always avoid extra non return valves for they don't stay non return for long, in hard limey water districts anyway. I find I get less trouble with vertical calorifiers with the PRV right on the top than the horizontal type. Also far less trouble if the calorifier is say mounted in an airing cupboard and higher up than the rest of the water system as it really needs to be, especially if a solid fuel stove is connected to it.

Regs bizzard.

Edited November 28, 2012 by bizzard

[n.b.Goldie]

Ahoy DD. Hope you and your landlady are well.

I don't have a calorifier as I have an air cooled engine and Paloma water heater but I work on boats with them and i've found that some boats have neither an expansion vessel nor regulator and they don't seem to have any more PRV blowing off trouble than boats with them, only when the valve becomes old and limescaled up. I think like electrics the more complicated the system the more trouble your likely to give. I always avoid extra non return valves for they don't stay non return for long, in hard limey water districts anyway. I find I get less trouble with vertical calorifiers with the PRV right on the top than the horizontal type. Also far less trouble if the calorifier is say mounted in an airing cupboard and higher up than the rest of the water system as it really needs to be, especially if a solid fuel stove is connected to it.

Regs bizzard.

 

Hi Bizzard.

 

Landlady and myself are well, hope you are too.

 

I also like to keep stuff simple, the less there is the less there is to go wrong.

 

Regards

Ditchdabbler