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Water Pump issues. Marine engineer wanted near Kinver/Stourbridge/BCN please?


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4 minutes ago, Ex Brummie said:

It matters not whether the system is in water. In fact, I can't think of any meaningful test to be done with an empty tank other than to check/replace the tank outlet valve. All other tests need to be done in water. As others have said, if the PRV does not leak then somewhere there is a bank of air acting as an accumulator.

 

A start would be to confirm or deny that with water in the system, the pump on and taps closed that once the pump cuts out it stays cut out for hours unless a tap is opened. Or if it keeps starting and running at much more frequent intervals while under the conditions above.

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8 hours ago, Tony Brooks said:

 

A start would be to confirm or deny that with water in the system, the pump on and taps closed that once the pump cuts out it stays cut out for hours unless a tap is opened. Or if it keeps starting and running at much more frequent intervals while under the conditions above.

I can confirm that with water in the system, the pump on and taps closed that once the pump cuts out it stays cut out for hours unless a tap is opened. The calorifier is horizontal.  I will be able to take naughty pictures of it tomorrow.

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8 hours ago, Cal Ando said:

I can confirm that with water in the system, the pump on and taps closed that once the pump cuts out it stays cut out for hours unless a tap is opened. The calorifier is horizontal.  I will be able to take naughty pictures of it tomorrow.

 

Thanks, that rules out any leaks. If this is a boat new to you I bet the calorfier has been installed twisted so the hot outlet is not right at the top. Even if it is then, depending upon the design, it can still be a beast to get all the air out. It might improve over time if you are lucky but if you are sure the pump inlet is clear I am 99% sure there is no actual fault, its just trapped air so you may have to live with it.

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Its trapped air in the horizontal calorifier which has the hot water outlet incorrectly positioned not at the top, had it before on a boat that was severely rocked craning out and the calorifier had rolled from its original position.

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2 minutes ago, Tony Brooks said:

Just realised even if the outlet is at the top, if its at the back of the calorifier the way boats tend to trim stern down would leave air trapped in the top front of the calorifier.

Very true.

Another reason why a horizontal calorifier is more problem than a vertical one, I never liked them. You never find them in domestic properties thankfully.

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3 minutes ago, Tracy D'arth said:

Very true.

Another reason why a horizontal calorifier is more problem than a vertical one, I never liked them. You never find them in domestic properties thankfully.

 

I also would never have one if it could be avoided. All the science points to vertical ones - and their concave bottoms makes them a little more long-lived when over pressured.

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1 hour ago, Cal Ando said:

Thanks guys.   Now how do I get my trapped air out.   And then how do I get it out of the calorifier?.   Why didn't it come out before.

Over a long period the air will get absorbed into the water. 

 

The hot  outlet of the calorifier must be the highest point.  So if it needs rolling or if the outlet end is low, raising it or the boat tipping whilst the hot taps are running. Fore and aft you could try filling or emptying tanks to get the floor more level.

 

A diagram of the layout and where the outlet is would help us.

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33 minutes ago, Tracy D'arth said:

Over a long period the air will get absorbed into the water. 

 

The hot  outlet of the calorifier must be the highest point.  So if it needs rolling or if the outlet end is low, raising it or the boat tipping whilst the hot taps are running. Fore and aft you could try filling or emptying tanks to get the floor more level.

 

A diagram of the layout and where the outlet is would help us.

 

As would the photos I asked for.

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3 hours ago, Tony Brooks said:

 

As would the photos I asked for.

Not just the calorifier its self and how its mounted but also the connections at the end, preferably with the camera/phone held level so we can see the angles involved. If you know the make that would also help.

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On 26/05/2021 at 20:36, David Mack said:

Why do you think replacing the PRV will make any difference?

 

On 26/05/2021 at 21:14, Tony Brooks said:

I suspect it won't

Thanks for all of your answers and I know it's difficult to diagnose faults by email.    I need a new PRV!

I returned to the boat for the first time this season, put some water in the tank, opened main tank output stopcock and the pump was still taking a long time to switch off when taps were closed.   I felt around the PRV and there were no leaks, however now the pump would not switch off at all with the taps closed.   Mystified, I felt around the PRV again and felt it move slightly.  Then ... see picture!

Yep, literally came off in my hand, couldn't tighten it back up,  but just thanked the Gods that water wasn't flooding out (can anyone explain why please?).  Adjustable spanner was too thick to fit under the cap and my spanner set only went up to 21mm - guess what AF size the flats were (22mm of course).   Finally forced the adjustable up under the cap against the valve spring and tightened it up only for pump to continue running.   Removed valve again, sealed threads with PTFE tape and lots of bad language, and refitted valve seat.  Pump now shuts off but still takes its time.   

 

No hot water coming from cold taps any more as far as I can tell and I also stripped and cleaned water pump filter, which needed doing.   This time I did forget to turn the main stop cock off and water flooded out.   Luckily, or by design, I'd fitted the pump inside a meat roasting dish for such events, so the water didn't go all over the bilges.   Basically ran frantically down the boat to shut off the stopcock and Mrs Calando and Calando-woof leapt aside for dear life.

This temp repair to the PRV will get us to Wigwam's.   There, a friendly engineer has agreed to dismantle the boat so that he can fit a new PRV valve as its on the bottom of the calorifier pipework.   We'll get the calorifier turned round properly this winter when we're at our home mooring.

Hoping a properly sealed PRV will resolve all my problems.

 

20210529_173319.jpg

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Pleased its sorted for now but the symptoms in total did not match that fault. The long time for the pump to turn of would be a symptom of a leak from the PRV or anywhere else but not the hot water out of a cold tap, that has nothing to do with faulty PRVs but does indicate air trapped somewhere acting as an accumulator AND that will also explain the pump taking a long time to turn off. What you found suggests it might be frost damage but a leaking PORV woudl cxaue nthe pump to keep turning on and off iwth the taps closed at more frequent intervals than normal..

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  • 1 month later...

Thanks for all your help and advice.

I finally contacted 'Days Afloat' who were initially mystified as the rest of us.   Lee didi an excellent job and has modified the system to look like Tony's classic system drawing.   

Non return valve fitted between tank and pump

Non return valve fitted between hot and cold feed

New PRV

Accumulator added to cold water feed

Expansion tank added to hot water feed

isolation valve between tank and pump moved so it can be accessed by normal human being and not elastoman!

 

system now works fine and according to spec

Thanks for everyone's help.

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