Author Topic: Strange water pump behaviour. (Read 7912 times)

Boatname · « **on:** June 26 2018, 20:31 »

Our boat has been ashore since last September and is being launched next Monday.

I am in the middle of system checking.

The water pump used to function exactly as you might expect.

Turn the tap on.

“Some” water would come out then the pump would kick in usually continuing for a second or two after turning the tap off, presumably recharging the system/ filling the accumulator tank.

“Felt” right.

Today was its second extended test where I probably got through 100 litres.

Now turning the tap on still gives instant water BUT the pump doesn’t kick in until about 2 litres has flowed through .. THEN after turning the tap off the pump keeps running, charging the system FOR THE SAME AMOUNT OF TIME AS IT WOULD HAVE RUN IF IT HAD BEEN RUNNING NORMALLY.

Apologies for the caps. but that is the vital part.

I didn’t time it (I will do) but you REALLY think that the pump is not going to kick in THEN you think it’s not going to turn off.

No air leaks, no bubbling or spitting from the 2 taps and 1 shower.

Ultimately you could say I don’t have a problem but I have learnt through the years not to ignore a different engine note, a change in the amount of pressure needed to do something.

This is one of those cases.

Any ideas?

See pics:

dawntreader · « **Reply #1 on:** June 27 2018, 07:57 »

That's 'normal' behaviour for the fresh water pump. There is pressure in the system (air in actuator bottle) and the water flows. When the pressure drops, the pump kicks in. Sometimes it will 'run on' to replace pressure.

Read this from the forum: http://bavariayacht.org/forum/index.php/topic,1080.msg5822.html#msg5822

Boatname · « **Reply #2 on:** June 27 2018, 10:24 »

Thanks for the link.

I’d like to ask the question another way.

Can you (and others) tell me either by actually timing it or doing it in your head now ... from opening a tap fully (hot, cold, in between... it makes no difference), how long does it take for the pump to start?

I categorically know that for the last 15 years it used to be around 2 seconds ... sometimes it was immediately, others perhaps 3 seconds, I suppose based on exactly how primed the circuit was. Yes it always should be but that’s what I had including the original pump and the replacement.... the first pump started leaking between the body and the fittings at the bottom.

I’m guessing at this moment it’s at least 10 seconds ... I put the timer on on my phone and kind of stared off into the middle distance imagining it.

My wife thought I was ill

Same pump as the last 5 years, same pump as the previous 10.

I go back to my statement that if something changes for absolutely no reason, check it.

Thanks

ps that link was particularly useful as perhaps only once a week ... usually at night ... the pump would blip (we live onboard for 5-6 months) and it always concerned me. Good to know I’m not alone.

MarkTheBike · « **Reply #3 on:** June 27 2018, 16:50 »

Hi Boatname
Yep, my pump kicks in between 1 - 2 seconds and runs on after shutoff for the same (1 - 2 secs). It sounds like an empty pipe somewhere, increasing the air volume. Is the calorifier filled? Definitely doesn't sound right.

Boatname · « **Reply #4 on:** June 27 2018, 17:18 »

Thank goodness Mark and thanks. I’m assuming the calorifier is full as the taps run cold for the amount of time you’d expect ... a bit like at home ... then the hot water arrives just as in the past.

But even with the tap set to fully hot the pattern is:

Cold water, warm to hot water, NO pump so it’s getting the pressure from the system then as stated after perhaps a 15 second delay the pump kicks in then continues when the tap is turned off.

Categorically no water leaks and if it was possible to have an air leak and NOT a water leak then there wouldn’t be enough residual pressure to run the tap.

Anybody else confirm their estimate of running time before the pump kicks in?

Thanks

MarkTheBike · « **Reply #5 on:** June 27 2018, 20:56 »

Are you sure the calorifier is completely full, without a big bubble at the top? If there is then you are effectively enlarging the pressure vessel. Also, the only time my pump doesn't kick in straight away is if the flow is less than full so could there be a constriction somewhere in the feed? Another thought - I didn't see in your posts whether you've done any work on the water system? Could it be you've fixed an air leak that you didn't know you had, so the system is now working properly where it wasn't before? Mine reacts quickly but I know I have a very slight leak somewhere, reducing the available 'push' from the pressure vessel.
Good luck...

Boatname · « **Reply #6 on:** June 27 2018, 21:38 »

Interesting thought re the calorifier being full. Not sure how I'd check it but I understand what you are saying ... that would provide a massive pressure reservoir compared to say the accumulator and yes the system would be charged.

Hmm.

Definitely not worked on any piping/plumbing EXCEPT I have changed the round shower covers on the transom which involved simply unscrewing one red, one blue and the shower pipe but having those ends open to atmosphere wouldn't cause a problem at the calorifier end and the shower exhibits exactly the same symptoms as the other two taps.

We are launching on Monday so I think I'll go wave jumping to see if the water in the cal moves around enough to have some effect.

Many thanks for the thought, perplexing as it is ... it has logic to it.

As usual I will report back.

ITIL MAN · « **Reply #7 on:** June 28 2018, 11:54 »

Same here my Bav 42 pump kicks in within 1 sec of turning any tap on and switches of the same when tap turned off.

Ricd · « **Reply #8 on:** June 28 2018, 15:40 »

Interestingly I had the same symptoms appear this season, after 6 years of normal operation (tap on, flow for a couple of secs then pump licks in until tap off plus couple of seconds). I also had some sort of airlock evident when filling the tank as the water would surge back out of the filler inlet, like a whale blowing off. Anyway, started filling tank more slowly which eliminated the back surge and interestingly also seems to have eliminated the strange water pump symptoms as outlined by the OP. I think my filling issue might relate to the breather which seems to be non-functional but not sure how that effects the water pump?

Boatname · « **Reply #9 on:** June 28 2018, 15:50 »

Thanks ITIL, timed it today ... tap open, water runs smoothly, no pump.

14 -15 seconds later the pump starts.

Turn tap off, pump runs for exactly the same period.

So, yes, I have a large pressure build up somewhere and the calorifier has to be the suspect.

Looking at this picture the cal. does seem to be high at the back ... but it always has been!

Undecided whether to leave it and hope being on the water solves it or start taking the easy fit connectors off ... which introduces air

I can’t see any harm being done, compressed air in the cal. vs REALLY hot water!

I’ll be back!

ps don’t worry about the non-standard fitting on the red pipe. Long story, temporary fix, replaced years ago.

Boatname · « **Reply #10 on:** June 28 2018, 15:56 »

Quote from: Ricd on June 28 2018, 15:40

Interestingly I had the same symptoms appear this season, after 6 years of normal operation (tap on, flow for a couple of secs then pump licks in until tap off plus couple of seconds). I also had some sort of airlock evident when filling the tank as the water would surge back out of the filler inlet, like a whale blowing off. Anyway, started filling tank more slowly which eliminated the back surge and interestingly also seems to have eliminated the strange water pump symptoms as outlined by the OP. I think my filling issue might relate to the breather which seems to be non-functional but not sure how that effects the water pump?

Now that IS odd. Last September I decided to take the water inlet and breather pipe off to give them a clean. I haven’t mentioned that as like you I can’t see how the two issues are connected. (sorry that reads badly)

However whilst my wife filled I had my head in the back of the boat watching for leaks and I could actually see the water flowing freely and heard the pre-gurgle

we get just before the tank fills. Same as the diesel tank.

How odd though that you had the same symptoms.

Ricd · « **Reply #11 on:** June 28 2018, 18:18 »

As I mentioned it seems to have resolved itself. Hopefully some bright spark will tell us how its all linked?
Good luck

MarkTheBike · « **Reply #12 on:** July 01 2018, 10:42 »

Quote from: Boatname on June 28 2018, 15:50

....Looking at this picture the cal. does seem to be high at the back ... but it always has been!....

Aha - so is it possible that, whilst sailing up a 20m wave mountain in the past

, someone below opened a hot tap and cleared out the bubble? Perhaps get a load of friends to stand at the stern to change the angle of the calorifier so any bubbles come out (obviously whilst running the hot tap). Whilst ashore, did anything happen to the tank so it sucked in air (pump service / loose connector / empty water tank / etc.)? If it turns out there is a bubble being the cause (and I can't think what else would cause the symptom), how realistic is it to level the calorifier?

Boatname · « **Reply #13 on:** July 01 2018, 11:50 »

Hi Mark. No pipes other than the filler/breather pipe were disconnected and there are no leaks.

The main water tank is always emptied for the winter with the hot tap open in the heads, cold tap in the galley and then the shower head is disconnected and the pipe drained then stored in the locker.

Yes I COULD release the calorifier clamps and lift it from the front but worry about disturbing all the other cut to length pipes.

The boat is launching tomorrow and even though they are very skilled there is still some movement.

I have a blue hose with an end cap on it in front of the engine. I understand this is to drain down the cal.

What I will do is cable tie it vertically and as high as it will go with the end off, and hope any air in the cal. vents.

Must remember not to turn the pump on

MarkTheBike · « **Reply #14 on:** July 02 2018, 19:03 »

Quote from: Boatname on July 01 2018, 11:50

Yes I COULD release the calorifier clamps and lift it from the front but worry about disturbing all the other cut to length pipes.

I wouldn't think it will need much lifting, 1/2 - 1 degree up at the pipes end should be enough. My pipes have enough play to lift about 20cm if necessary (not that it would fit under the bunk if I did). Stick the level along the straps, loosen the front strap bolt, lift the (still empty!) calorifier and slide some flexible plastic strips under the tank, enough to move the level bubble up to the front line. That should be about 1 degree. Trim the plastic as required and refasten the clamp.

Quote from: Boatname on July 01 2018, 11:50

I have a blue hose with an end cap on it in front of the engine. I understand this is to drain down the cal. What I will do is cable tie it vertically and as high as it will go with the end off, and hope any air in the cal. vents.

I wouldn't worry about that too much if you have the tank slightly uphill, it should vent naturally.

p.s. after all this, if it still takes 15 secs then I'm stumped...

Jeff Jones · « **Reply #15 on:** July 02 2018, 21:40 »

Hi Boatname..

not sure if this helps shed some light on your problem..

From the pump info shown in your photos shows 11LPM or 2-2.6litres (in 14-15secs) so you'd think there would be 2L of air somewhere in the system which suggests air being compressed and giving the symptoms.

Have you tired opening all the taps at the same time?
or turning off the pump whilst running the tap piped the nearest to the clarifier and see if it will bleed out the air.

From my own B34 the clarifier points downwards to the outlet - so my money would be on a couple of litres of air in the top of the clarifier.

Jeff

Boatname · « **Reply #16 on:** July 03 2018, 23:10 »

Jeff, Mark, many thanks keep losing WiFi trying to reply. Update later

Boatname · « **Reply #17 on:** July 04 2018, 09:07 »

Jeff/Mark

Thanks for the thoughts.

We had a really rough night here weather wise on Monday, ideal for “shaking things up”

I agree air has to be trapped in the calorifier bit am confused why as many years ago we had a problem with a leak around the element which involved taking it out probably 5 times over the course of a season trying to find a gasket that fit and solved the problem.Eventually found that the face the gasket screws to had a really slight score in it (had to be done when manufactured) and managed to flat it off, not had a leak since.

The point of that is the cal. was literally emptied into the bilges and was totally open to the air whilst the element was out.

Every time I refilled it, it did just that. Refilled. No air locks.

Hence my confusion.

Monday I turned off the element and the pump.

Opened the hot tap in the heads.

Opened the cold tap in the galley.

Left them like that overnight.

It was noticeable that the cold tap ran out of water/pressure very quickly (as you’d expect) but the hot tap ran for possibly 10 seconds albeit at very low pressure ... just ran and ran.

Tuesday turned on pump, left taps open until both running ok (they are never as powerful with both open as just one ... I understand that) and for a while all seemed good but it didn’t take long for the issue to reappear which is mind boggling for me.

If there was an air leak then surely water would drip, the pressure would drop, the pump would blip. But nothing.

It all works fine EXCEPT for the 15 seconds of calorifier pressure.

I’m going to leave it this week as we are living on the boat but next week I’ll try lifting the cal. (but see above ... it’s been physically open around 5 times plus of course the first time it was ever filled) and .... well I don’t know after that.

Live with it?

I can’t see it doing any harm. Isn’t having air under pressure pretty much the same as hot water under pressure? Yes I know air compresses.

I just don’t like ignoring things out of the norm. I have found through experience there’s normally a negative reaction down the line.

Thanks again for your continued support.

Apart from the risk of 100+ litres in the bilge this isn’t exactly life threatening but just so confusing.

MarkTheBike · « **Reply #18 on:** July 04 2018, 15:14 »

Quote from: Boatname on July 04 2018, 09:07

Apart from the risk of 100+ litres in the bilge this isn’t exactly life threatening but just so confusing.

Hi Boatname

Confusing is the word after what you've said about the work previously. The only thing I can think of is, at the time, the trim was bows-up, e.g. anchor / chain off the boat; empty forward water tank + people all aft; etc., so that the calorifier was actually slightly nose-up. Of course, the initial bubble would be cold. Each time the water was heated, the bubble would expand and the excess would go down the pipe if the taps were opened. The bubble would reduce in time, especially if that happened when it was a bit lumpy. Apart from that, I'm stumped. All that's left is to heat the water, lift the calorifier at the front, open the hot tap and see if it clears. You should only have to do that once if, as you say, there's no other leaks and it could be re-strapped as before. Actually, another thought (re: leaks) is that the system is only pressurised downstream of the pump but not upstream between the tank and the pump. If there's a leak in, say, one of the connectors above the tank water level, it's possible that air may be sucked in when the pump runs but no water would drip when it's off. That could result in a bubble in the calorifier. Just a thought...

Ricd · « **Reply #19 on:** July 05 2018, 20:59 »

One final suggestion. Empty system as if winterising, and refill again from scratch.

Boatname · « **Reply #20 on:** July 06 2018, 15:51 »

Thanks Ric, just tried that including taking the end off the calorifier drain pipe and filling that pipe with water before putting the end back on.

Absolutely the same

Next it will be lifting the tank but really can’t understand why.

Thanks all for your suggestions, I’ll post again if I sort it (and know how)

dawntreader · « **Reply #21 on:** July 07 2018, 08:00 »

Just a thought, but if you filled the accumulator bottle with water (i.e. expelled all air) and then tried running the pump that might identify that there is a separate source of air being compressed?

At least you will know then....

Boatname · « **Reply #22 on:** July 07 2018, 20:15 »

Thanks for the thought but the water comes up level with the word Comet so there really isn’t much air in there and as I have to turn it upside down to remount it I would probably lose that amount of water in the process.

It was 30 degrees inside my boat yesterday so not planning any more investigation until it’s cooler at which stage I will go for the only thing left ... tilt the calorifier, but although an air bubble in there would explain everything it wouldn’t explain that the immersion has been out previously and the system recharged fully.