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


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Hi.   Can anyone recommend an engineer who can work on domestic water systems for our NB.   Ashwood Marina cannot help and we need to get to Napton (Wigrams) via Stourport, Netherton, Kingswood & Lapworth.   The water pump runs for excessively long periods before pressurising (e.g. 40 secs) and hot water comes out of cold taps for a few secs.   We are in the unique situation of still having the calorifier drained down for winter.   The symptoms are:

Open a tap and after few secs as normal, pump cuts in, but them takes about 40 secs to shut off after tap closed.

1) Didn't do this before we ran out of water on Trent & Mersey (Oct last year 1 month before winterising)

2) pump takes long time to pressurise

3) Engineer on the Trent & Mersey looked at system whilst on our way to Ashwood and failed to fix it.  Claimed main tank blockage, pump failure, NR valve failure, filter blockage, system leak, split calorifier.   No major leaks detected, No blocakges detected, fitted new pump which didn't fix issue, charged loads of money for failing to fix, I manage to fix the leaking hoses after he'd fitted the new pump!

4) Hot water comes out of cold tap for about 15 secs when pump cuts in.

5) Actuated PRV on calorifier and beaten 6 bells out of housing to try and loosen any scale on the seat.

6) The system does NOT have an accumulator

 

I'm thinking this might require a new PRV and if so, now, with the system drained, would be a good time to change it.   Only worry I have is introducing leaks when system is filled.  Any other ideas are welcome!

If anyone knows anyone who could diagnose and fix this issue I'd be most grateful.

 

Whilst we're here,  anyone know a boat builder/carpenter who could replace aft steps, bed and create a Pulman dinette?

TIA

 

Edited by Cal Ando
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No help for an engineer but something seems not right with your understanding of what has been done.

 

Calorifier still drained down yet you are pressurising the cold water system? Its not impossible but I have yet to see a boat with a shut off valve on the inlet to the calorifier. If it has no such valve then the water system would try to fill the calorifier but unless you let the air out of via the hot taps then it would act as a giant accumulator so water would partially fill it, that water could get heated by the engine or C/H coils and with no calorifier inlet  non return valve you could get hot water out of cold taps.

 

The calorfier acting as an accumulator would  explain the long time for the pump to cut out because of the much larger volume compared with an accumulator.

 

Try turning all the hot taps on and see what happens.

 

Edited to add, you might have two water pumps as many hire boats but typically they are not hot and cold, they are working and spare. If so having one tuned off may well not stop water entering the calorifier.

 

 

Edited by Tony Brooks
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I think Tony has probably got it. Half empty calorifier.  I get a similar issue if the tank runs dry, nothing works properly and loosening hose clips here and there works eventually but with my simple system sucking the kitchen tap works, yours is likely to be more complex but its worth a try.

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8 hours ago, Cal Ando said:

No blocakges detected

Probably what @Tony Brooks says, the empty cauliflower is acting as an accumulator. Similar experience to @Bee, where air trapped in the top of the calorifier will make the pump run on for ages till it has been purged out by running the hot tap. 

However, you say no blockages detected. How do you know? The tank running empty may have drawn debris that has partially blocked the exit pipe. If you have an integral mild steel tank, this is not uncommon. Is there a pre filter upstream of the water pump? Has this been cleaned/checked? Usually they have a transparent lid so you can see any debris blocking the mesh.

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8 hours ago, Cal Ando said:

We are in the unique situation of still having the calorifier drained down for winter.

 

8 hours ago, Cal Ando said:

4) Hot water comes out of cold tap for about 15 secs when pump cuts in.

 

If you are getting hot water then the calorifier cannot be completely drained. As others, I suspect it is part full and acting as an enormous accumulator.

Since we are now past the risk of frost I would just fill the calorifier by opening hot taps and letting the water run until free of air. With a bit of luck hot and cold water systems should be fine after that.

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So sorry for misleading everyone!  All these symptoms occurred BEFORE the calorifier was drained for the winter but after it ran out of water on our journey.   However, what Tony and Bee say makes sense as someone else said before we left it over winter  that the calorifier was acting as a giant accumulator.   We're going up to the boat this w/e so hopefully a complete refill of the system might cure it or bring more symptoms.  Thanks for the advice re sucking air out via hot tap.   PS no blockage between tank and pump as pipe was removed and checked, but thanks to Jen-in-Wellies for this suggestion.

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19 minutes ago, Cal Ando said:

So sorry for misleading everyone!  All these symptoms occurred BEFORE the calorifier was drained for the winter but after it ran out of water on our journey.   However, what Tony and Bee say makes sense as someone else said before we left it over winter  that the calorifier was acting as a giant accumulator.   We're going up to the boat this w/e so hopefully a complete refill of the system might cure it or bring more symptoms.  Thanks for the advice re sucking air out via hot tap.   PS no blockage between tank and pump as pipe was removed and checked, but thanks to Jen-in-Wellies for this suggestion.

And the reason the hot comes out of the cold tap is no or a stuck check valve in the cold feed to the calorifier.

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1 hour ago, ditchcrawler said:

And the reason the hot comes out of the cold tap is no or a stuck check valve in the cold feed to the calorifier.

 

But may well stop once there is no air in the calorifier or hot pipes.

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2 hours ago, Cal Ando said:

So sorry for misleading everyone!  All these symptoms occurred BEFORE the calorifier was drained for the winter but after it ran out of water on our journey.   However, what Tony and Bee say makes sense as someone else said before we left it over winter  that the calorifier was acting as a giant accumulator.   We're going up to the boat this w/e so hopefully a complete refill of the system might cure it or bring more symptoms.  Thanks for the advice re sucking air out via hot tap.   PS no blockage between tank and pump as pipe was removed and checked, but thanks to Jen-in-Wellies for this suggestion.

A few years ago I had a newly built narrowboat with a plastic/polypropylene water tank.

 

Soon after delivery the water pump would take a long time to pressurise the system. It turned out to be a small piece of plastic swarf stuck in the inlet port of the water pump filter. The inlet hole in the actual filter casing was much smaller than the diameter of the water pipe that supplied the filter from the water tank. The filter mesh in the filter was fairly clean but it was only by taking the pump off and examining it very closely that the swarf was detected. I needed a pair of tweezers to extract the swarf.

 

I was surprised that the inlet hole in the pump case moulding was so small and that such a small piece of debris could cause such a problem.

 

 

As the problem occurred immediately after running out of water, and just out of interest:-

 

What type of water tank do you have? Integral mild steel, plastic or stainless steel

 

Does the system still have the new water pump that the engineer fitted or was the new pump just fitted for diagnostic purposes and then removed?

 

Is there a separate filter between the tank and the water pump?

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Thanks Arbutus.

The water tank is stainless, the replacement water pump is currently in the system(but is same model as original) and there is a small filter in the inlet of the water pump wot I have taken off and washed!?

Unless anyone has any better ideas, I'll drive over to Midland Chandlers and buy a new PRV .   If my pump delivers 35 PSi (i.e. 2.4 bar), do I get a 3 bar or 4 bar PRV.  I don't know what's on there at the moment and hope to waste as little time as poss swapping it out.

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30 minutes ago, Cal Ando said:

Thanks Arbutus.

The water tank is stainless, the replacement water pump is currently in the system(but is same model as original) and there is a small filter in the inlet of the water pump wot I have taken off and washed!?

Unless anyone has any better ideas, I'll drive over to Midland Chandlers and buy a new PRV .   If my pump delivers 35 PSi (i.e. 2.4 bar), do I get a 3 bar or 4 bar PRV.  I don't know what's on there at the moment and hope to waste as little time as poss swapping it out.

 

I would suggest that you go to a plumbers merchant, less chance of a marine markup.

 

The PSI on your existing PRV should be marked but its never a good idea to overstress the calorifier, especially as you seem t have no accumulator/expansion vessels, so I would go for 3 but be prepared to change it f water hammer bounces it

Edited by Tony Brooks
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2 hours ago, Cal Ando said:

Thanks Arbutus.

The water tank is stainless, the replacement water pump is currently in the system(but is same model as original) and there is a small filter in the inlet of the water pump wot I have taken off and washed!?

Unless anyone has any better ideas, I'll drive over to Midland Chandlers and buy a new PRV .   If my pump delivers 35 PSi (i.e. 2.4 bar), do I get a 3 bar or 4 bar PRV.  I don't know what's on there at the moment and hope to waste as little time as poss swapping it out.

Is there water coming out of your PRV?

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There has been no mention of frequent turning itself on and off once up to pressure so that rules out leaks, even back leaks through the pump valves and the PRV.

 

Assuming the hot system has been properly bled it leaves us looking for reasons why it takes a longer time to reach cut out pressure so lack of pump output but why?

 

1. One or more pumping chambers not operating (split diaphragm/faulty valves) but its a new pump.

2. Partially blocked inlet to pump but the OP says he has cleaned the inlet strainer so if it is a blockage its else where.

3. Air leak into inlet pipe system but less likely because usually the pump is below full tank level .

4. Pump not spinning fast enough but a pump motor fault unlikely because its a new pump so that leaves us with low voltage at pump.

 

Apart from taking a very close look at the complete inlet system, I think the OP needs to report back the voltage at the PUMP with the pump RUNNING.

 

 

 

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

I suspect it won't

Hi Tony.   I'm suspecting the PRV valve because I read your training page viz:

Continual leaks from PRV

If the PRV drain is leaking all the time it indicates one of three faults:-

Pump pressure switch failed or set too high.

Leaky PRV valve seat.

Faulty PRV

The latter is not that common.

The PRV Knob

The PRV normally has a plastic knob on top. This looks as if it is some form of adjustment. In fact it is a device that lifts the valve off its seating every time you turn it and it clicks.

If the pump keeps running and there is a constant leak from the PRV drain hose it may well be caused by scale caught on the valve seat.

Twist the knob a few times with the pump on to try to flush the scale from the seat.

PRVs are not normally adjustable.

Always fit a PRV with a lower pressure rating than the calorifier – typically between 2 and 2.5 bar (30 to 37 psi).

 

 

as the pump keeps running, and my home engineer suggested that there may be crud in the valve seat, I'm suspecting the PRV, But opening it doesn't make any difference.  hence the PRV is either nothing to do with the issue or it is so stuck it needs changing.  I couldn't tell or remember whether it was passing water constantly as the outlet is a skin fitting.  I'll run the pump and look outside when we go tot the boat tomorrow.   The pump is running at its usual speed, batteries are all fine and current draws are normal so I'm not suspecting low voltage to the pump.    

Does my reasoning with the PRV make sense or would you still suggest leaving it alone?

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Thanks to everyone for their thoughts and suggestions so far.   

One last question for now.   as the symptoms occurred last year before the system was drained and winterised, we are in the unique situation of having a 'reset' scenario on the whole system.   I.e. tank empty, calorifier empty, all lines and taps empty/isolated (in theory).   Can anyone suggest any tests (apart from TB's idea to check the voltage which I shall do) whilst the system is drained and /or before or as the system is filled.   I don't want it down too long as I want some tea!   Also if I change the PRV is there a better time?

 

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6 hours ago, Cal Ando said:

Hi Tony.   I'm suspecting the PRV valve because I read your training page viz:

Continual leaks from PRV

If the PRV drain is leaking all the time it indicates one of three faults:-

Pump pressure switch failed or set too high.

Leaky PRV valve seat.

Faulty PRV

The latter is not that common.

The PRV Knob

The PRV normally has a plastic knob on top. This looks as if it is some form of adjustment. In fact it is a device that lifts the valve off its seating every time you turn it and it clicks.

If the pump keeps running and there is a constant leak from the PRV drain hose it may well be caused by scale caught on the valve seat.

Twist the knob a few times with the pump on to try to flush the scale from the seat.

PRVs are not normally adjustable.

Always fit a PRV with a lower pressure rating than the calorifier – typically between 2 and 2.5 bar (30 to 37 psi).

 

 

as the pump keeps running, and my home engineer suggested that there may be crud in the valve seat, I'm suspecting the PRV, But opening it doesn't make any difference.  hence the PRV is either nothing to do with the issue or it is so stuck it needs changing.  I couldn't tell or remember whether it was passing water constantly as the outlet is a skin fitting.  I'll run the pump and look outside when we go tot the boat tomorrow.   The pump is running at its usual speed, batteries are all fine and current draws are normal so I'm not suspecting low voltage to the pump.    

Does my reasoning with the PRV make sense or would you still suggest leaving it alone?

 

Is your pump running all the time or even turning itself on and off  when the Taps are closed more frequently than it did before running out of water? If the answer is yes where where did you say that? All I have read is that it takes a long time for the pump to cut out and then takes about 40 seconds to cut out again when it runs with a tap open.

 

Any sort of leak be it internal back through the pump valves or external vis pipe leaks, dripping taps, split calorifier or a leaking PRV will cause the pump to run more frequently that it once did with  the taps closed. The shorter the time between pump runs the worse the leaks.

 

Without the more frequent pump running then you are normally looking at  a lack of flow from the pump for whatever reason, those I listed in my last post.

 

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6 hours ago, Cal Ando said:

Thanks to everyone for their thoughts and suggestions so far.   

One last question for now.   as the symptoms occurred last year before the system was drained and winterised, we are in the unique situation of having a 'reset' scenario on the whole system.   I.e. tank empty, calorifier empty, all lines and taps empty/isolated (in theory).   Can anyone suggest any tests (apart from TB's idea to check the voltage which I shall do) whilst the system is drained and /or before or as the system is filled.   I don't want it down too long as I want some tea!   Also if I change the PRV is there a better time?

 

 

One longer shot than fits you symptoms apart from the fact you would not suffer such symptoms immediately after refilling the tank is a blocked water tank breather would gradually reduce the pump output as you drew water from the tank and built up a depression in the tank. Removing the filler cap and seeing if the symptoms go away would rule that one out.

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Another thought. What sort of tank isolator valve do you have? If its a wheel turn gate valve It  has been known for the gate to fall off or scale preventing it closing properly so if you closed it when prepping for winter it may not  be fully open.

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9 minutes ago, Tony Brooks said:

Another thought. What sort of tank isolator valve do you have? If its a wheel turn gate valve It  has been known for the gate to fall off or scale preventing it closing properly so if you closed it when prepping for winter it may not  be fully open.

Still not sure that would explain hot water cycling back through the cold tap, and think your suggestion of a large cushion of air in the calorifier is the answer. 

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7 minutes ago, BWM said:

Still not sure that would explain hot water cycling back through the cold tap, and think your suggestion of a large cushion of air in the calorifier is the answer. 

 

It won't but the symptoms as given do not fit a PRV problem.  Although we have not been told explicitly that all the hot taps have been left running for a while the OP has implied that the system has been in use with this fault for dome time so I can't see a vertical calorifier being the problem but a horizontal one, especially if its been fitted twisted over, could easily have a lot of air trapped in the top.

 

So vertical or horizontal calorifier and if horizontal photos of where the pipes go onto it showing the hot outlet pipe.

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11 hours ago, Cal Ando said:

Hi Tony.   I'm suspecting the PRV valve because I read your training page viz:

Continual leaks from PRV

If the PRV drain is leaking all the time it indicates one of three faults:-

 

So is your PRV continuously leaking?

If not the PRV is a complete red herring.

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15 hours ago, Cal Ando said:

Thanks to everyone for their thoughts and suggestions so far.   

One last question for now.   as the symptoms occurred last year before the system was drained and winterised, we are in the unique situation of having a 'reset' scenario on the whole system.   I.e. tank empty, calorifier empty, all lines and taps empty/isolated (in theory).   Can anyone suggest any tests (apart from TB's idea to check the voltage which I shall do) whilst the system is drained and /or before or as the system is filled.   I don't want it down too long as I want some tea!   Also if I change the PRV is there a better time?

 

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.

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