Air lock

[vauxhall25]

I have a condensing boiler with separate hot water cylinder adjacent on the ground floor. The house is 20m long so I have to have an electric pump for the domestic hot water. When the hot water is switched on ie for a shower the pump comes on automatically and switches off when the shower etc. is turned off. However somehow air has got into this system so that when the shower etc. is switched off the pump comes on by itself for 30 seconds or so and repeats this for about 5 minutes or more(sometimes 15 minutes). Has anyone any idea how this problem can be fixed? I have had an experienced plumber to try and fix it but to no avail.

 

[Madrab]

Are you talking about a normal open vented cylinder with a shower booster pump?

Is it a universal (negative head) pump?

 

[vauxhall25]

Thanks for responding. Being a non plumber I am not sure what an open vented cylinder is, all I can say is that it appears to be a normal cylinder with a vertical pipe with a red plastic top about half way up. It is not a shower booster pump, the pump operates on all the hot water outlets.
Again I do not know if it is a negative head pump, all I can tell you is what is written on the pump(which is a free standing plug in pump with what I am guessing is a hot water feed in and out of it). It is a Salamander pump,part number M370WTO5,model 96-021C 38 range IPH 370W 230V 50HZ 2800RPM class F 2.5A 10uf 400V capacitor. Hoping you can make sense of this!

 

[trojanhawrs]

What makes you think it's airlocked? Is there a non-return valve on the discharge side of the pump?

 

[vauxhall25]

Not sure what one of those looks like but I would say not. There is a small chamber on top of the pump with 32psi written on it. I believe the system is airlocked because the plumber who tried to fix it seemed to think that was the problem, however there are no leaks where air could get in. The only other possibility he came up with was something to do with the hot water cylinder.

 

[Madrab]

Pictures please - if there's a small chamber on top of it then that could be the expansion vessel of a universal (negative head) pump

What make is it? does it look something like this?

 

[trojanhawrs]

It's a salamander he says, think it might be one of these

 

[vauxhall25]

It is what trojanhawrs is saying, a Salamander pump, either a CT Force 20 SU or 30SU

 

[trojanhawrs]

As madrab says check the vessel.
Unplug the pump. Screw the valve cap off, it's like a bike or car tyre valve. Give it a wee press with a small screwdriver or your fingernail, If water comes out the bladder is burst and vessel needs replaced. If air or nothing comes out put your bike pump on it and inflate to 32 psi.

 

[vauxhall25]

Will try this although need to get hold of a psi gauge first

 

[Madrab]

I have had an experienced plumber to try and fix it but to no avail.

If it does turn out to be the EV, then I'm afraid to say he aint very experienced, at least with shower pumps

 

[vauxhall25]

So ...............having got a pressure gauge and tested the pump pressure it was where it should be. So not that which is the problem. Any other ideas?

 

[Madrab]

Slow leak somewhere - weeping tap

 

[trojanhawrs]

Just to clarify, it's happening right after you use the shower etc and turn it off yes?
Do you have an isolation valve on the suction side of the pump?

 

[vauxhall25]

Yes it is. When you turn off the tap/shower the pump stops then starts again a few seconds later. And yes there is an isolation valve on both the pipes that run into and out of the pump