Shower runs hot and cold intermittently

[millsthings]

Hi there,

I have a shower, which gets its water from the hot water tank and cold-water tank via a pump, which sits under the bath to boost the water pressure.

The shower water will not remain at a constant temperature.

I think the cause is due to air in the hot water cylinder or pump.

Q: How do you remove air trapped in a hot water cylinder? The only bleed value I see is running from the triple value (I think that is what it is called) but this has no air trapped. Should there be another value located somewhere near the top of the cylinder or is there a technique for clearing trapped air out of cylinders or central heating systems?

 

[ChrisR]

It won't be trapped in the cylinder, there's a vent pipe going up, to let it out. And its down that pipe that your air is probably getting onto your shower. Sorry don't know what you mean by a "triple value".

How is the hot water fed to the pump - is it from a special pipe or just the one which used to go to the taps? What pump is it?

I expect that

• 1) if you keep the flow of hot water down the problem will not appear
  
  2) it ain't plumbed right

 

[millsthings]

The pump is a watermill low voltage SS450DLV

The hot water is fed from the top of the hot water cylinder in its own pipe directly down to the pump.

I think it is plumbed correctly as I have the original pump installation guide and the actual plumbing does look as it should.

I have reduced the flow of hot water by about a third as the value was fully open. I think it has made a difference but will give it a full test in the morning when I have my shower. I don't quite trust it yet

Thank you very much for your advice. Most appreciated.

 

[millsthings]

unfortunately reducing the hot water through put has not solved the problem but it has made it less of a temperature change so it is better than it was.

I forgot to mention before that when the water changes in temperature the pump changes tone.