Pump problem (I think!)

[bclondon]

Hi to everyone...
1st post so please be gentle.
We have an old baxi boiler heating 6 radiators..hot water is via a multi-point water heater. The water is pumped round by a Myson pump on 1st (slow) speed. Boiler has been regularly serviced. Heating has always been very reliable if not (swishing) noisy at times.
We are in a basement flat & the small expansion tank is just below the ceiling in the corner of a room.
We noticed that the bathroom radiator/towel-rail was cold at the top. Bled the radiator & the boiler would fire up fine but for some reason the pump does not seem to be pumping although it makes pumping noises if you see what I mean. After a minute or so the boiler cuts out...restarting the boiler via the room-stat a couple of times seems to get the pump working & then all is fine. Once air is back in the bathroom radiator (after 1/2 days) the boiler works fine too! There is lots of swishing (air) noise when the pump is working & occasionally you hear a minor blowing noise coming from the expansion tank. Have checked the water level in the expansion tank & that seems fine.
Is the pump faulty (sticking) or is the air in the system the problem?
I have read about sludge being a possible cause of air problems & maybe the expansion tank too but as we live in a deep basement to drain the system will not be easy.
Any thoughts or suggestions would be welcome.
Very many thanks.

 

[grahamgas]

There may be a very small leak/fitting lose in the system that is pulling air in somewhere.

 

[Billy Bob Bob]

are you having water erupt into the tank and the boiler sounding like a large kettle?

 

[bclondon]

There may be a very small leak/fitting lose in the system that is pulling air in somewhere.

Thanks for that.
How is it that with air in the radiator the pump keeps pumping 1st time every time! Yet when I bleed the radiator the pump refuses to work properly. I then have to switch (via room-stat) the boiler off, let it cool down & re-start sometimes 2/3 times before the pump kicks in & stays on.
Boiler seems to work 100%, it simply cuts out if the pump refuses to work properly & then re-starts when it's cooled down & cuts out again if the pump has still not kicked in.
Seems crazy that taking air out of the system stops the pump working.
Does it sound like the actual pump maybe faulty & for some (reduced/increased pressure?) reason having air in the system makes the (faulty) pump work?
It's driving us nuts.
Thanks for helping all the same.

are you having water erupt into the tank and the boiler sounding like a large kettle?

Mark thanks.
When it starts there is a huge rushing water sound from the boiler (pump sits under it) and occasionally a sort of blowing noise from the expansion tank. Boiler is very quiet..no sounds of a kettle boiling, flame looks a very healthy blue too.

 

[Billy Bob Bob]

sounds like the pump is sticking,the boilers cutting out because the stat on the boilers kicking in due to it not being able to dissipate its energy you need a new pump in regards to the air this can be sevaral reasons but when the pump sticks cavitation is taking place(venting over) and inducing air the next time you get air in the rad CARFULLY!!! try setting it on fire if it burns its a by product of corrosion not air

 

[bclondon]

sounds like the pump is sticking,the boilers cutting out because the stat on the boilers kicking in due to it not being able to dissipate its energy you need a new pump in regards to the air this can be sevaral reasons but when the pump sticks cavitation is taking place(venting over) and inducing air the next time you get air in the rad CARFULLY!!! try setting it on fire if it burns its a by product of corrosion not air

Thanks Mark.
So a new pump for sure.
What do you mean by corrosion. Is that in the radiators or boiler..how does it effect the operation of the system?
Does 'cavitation' also draw air into the system?
Sorry to sound so dumb but might a new pump which works 1st & every time solve the problem?!

 

[Billy Bob Bob]

yes cavitation does draw air into the system but its probably badly corroded as well,a new pump will help but corrosion will wreck it i would consider a de scale as well

 

[bclondon]

yes cavitation does draw air into the system but its probably badly corroded as well,a new pump will help but corrosion will wreck it i would consider a de scale as well

Thanks again Gas Man..
Although the boiler is well maintained the system is old (35years +) so not sure if it would survive a de-scale! Hopefully a new pump will keep us warm for another winter!

If in the future we bit the bullet & went for replacing the boiler & linking the hot water with say a condensing boiler should we replace all the old radiators too? Is there some sort of pressure test that can check the pipework could take a pressured system?
Finally any ideas on finding an honest plumber/fitter to fit the new pump..we live in London?
Thanks again for all the advice..really do appreciate it.

 

[moony]

if the rads are 35 yrs old and the boiler is an old one too then get a new system matey....

youve had a good innings with that system. and well done for maintaining it - its probably the reason youve had so many years service out of it.

Thanks again Gas Man..
Although the boiler is well maintained the system is old (35years +) so not sure if it would survive a de-scale! Hopefully a new pump will keep us warm for another winter!

If in the future we bit the bullet & went for replacing the boiler & linking the hot water with say a condensing boiler should we replace all the old radiators too? Is there some sort of pressure test that can check the pipework could take a pressured system?
Finally any ideas on finding an honest plumber/fitter to fit the new pump..we live in London?
Thanks again for all the advice..really do appreciate it.

a pump is really not hard to change yourself - and if your getting a plumber in to change it you shouldnt get ripped off me old mate, its a straight swap. 80 squid for pump (groundfos) and a hours labour.

 

[ecowarm]

could just be out of water, check ball valve not stuck in f&e tank.
Eco

 

[bclondon]

if the rads are 35 yrs old and the boiler is an old one too then get a new system matey....

youve had a good innings with that system. and well done for maintaining it - its probably the reason youve had so many years service out of it.
a pump is really not hard to change yourself - and if your getting a plumber in to change it you shouldnt get ripped off me old mate, its a straight swap. 80 squid for pump (groundfos) and a hours labour.

Thanks for info especially approx cost of pump & fitting.
If we went for a new system could we safely use existing pipework (new radiators boiler etc) to save tearing up lovingly sanded & sealed floors throughout? Is there a way to pressure test pipework?
Really grateful for help

could just be out of water, check ball valve not stuck in f&e tank.
Eco

Thanks ecowarm but that was my first check..plenty of water & ball valve is working well.
Air is now back in the system (v/top of bathroom rad cool) but pump is kicking in 1st & every time..all the other rads get piping hot..still lots of swishing sounds.
To repeat an earlier question is there any technical reason why with air in the system the pump strangely works 1st time? Feeling reluctant to bleed the rad as every time I do the pump refuses to work..takes 2/4 attempts to get it pumping properly.
Thanks again

 

[moony]

old pipe work could be used but again i would have new, purely the reason its been in so long and on a pressurised system any pin holing will be increased.

yes you can test the pipework, plumber could do this - but again it doesnt mean it will not go with prolonged pressure.

if ripping up the floor is a no no then surface pipework or drops from above could be installed - theres ways round everything just depends how much you want to spend to get walls chased etc etc.

people will quite happily spend 15grand on a car that will lose the cost of a heating installation in value in its first year.... crazy, when you think that we should be putting a warm house and water as top priority.

 

[bclondon]

old pipe work could be used but again i would have new, purely the reason its been in so long and on a pressurised system any pin holing will be increased.

yes you can test the pipework, plumber could do this - but again it doesnt mean it will not go with prolonged pressure.

if ripping up the floor is a no no then surface pipework or drops from above could be installed - theres ways round everything just depends how much you want to spend to get walls chased etc etc.

people will quite happily spend 15grand on a car that will lose the cost of a heating installation in value in its first year.... crazy, when you think that we should be putting a warm house and water as top priority.

Thanks for the sensible advice.
Still would like to know why the pump is pumping 1st time now air is in the system again.
Any ideas please

 

[bclondon]

Thanks for the sensible advice.
Still would like to know why the pump is pumping 1st time now air is in the system again.
Any ideas please

Just had an honest plumber call & the problem was a blockage on the T junction going into the pump from the mains water. He cleverly created an airlock in expansion tank to enable him to access the T (without draining the system) cleaned out all the gunge in the pipes & bobs your uncle. He's put some Sentinel inhibitor into the expansion tank..serviced the boiler too. Pump is fine & touch wood the boiler is as quiet as a mouse!
Thanks again for everyone's help & advice.

 

[doitmyself]

when the pump sticks cavitation is taking place(venting over)

Cavitation and venting over are not the same thing.