Shower Pump Air in system problems

[Paul847673]

Hi

I am looking for some advice I have a grundfos twin impeller 1.5 pump on a gravity fed system.

I have recently replaced the pump along with the shower mixer bar and head as when turning the shower on it would start up and then the water pressure would drop and the pump would become noisey.

The pump has been working for a few years before I encountered this problem. Pump is located next to tank in the cupboard with the piper work going into the loft then back down to the shower. It has a Surrey flange on the top of the tank.

I had a plumber out who seemed to think it was air getting into the system, I tried forcing the air out by covering the tap when the hot and cold both open but this did not work. I then removed the mixer bar and turned the shower on and it worked fine.

After replacing the pump and shower mixer it worked fine for a few weeks then the problem started again!

I can hear air but can't seem to keep it out. I don't have any air vents or non return valve on the pipe work.

This is driving me mad so any advice would be appreciated!

Thanks

 

[HERTS P&D]

Is your float valve in the cold water tank faulty?

Andy

 

[Paul847673]

funnily enough I replaced it myself about a year ago and I mentioned it to my plumber but he dismissed it.

How would I know if it is faulty?

 

[HERTS P&D]

Is it working when the shower/bath is in use?

Andy

 

[Paul847673]

Well the float valve seems to be working but I had to bend the arm with the float a while ago to stop the overflow from dripping through the night.

I just can't understand how it has worked for a few weeks with a new pump and shower mixer but has now filled with air again. Air also seems to build up if the shower hasn't been used for more than a day.

 

[Paul847673]

So this morning I went into the loft while the shower pump was on and checked to see what the float valves were doing.

I had the shower mixer set to 38 degrees.

I have got 2 tanks in the loft and the float valve were the dedicated inlet to the pump goes to did not do anything for a while, they only time it really started was when I changed the thermostat on the mixer bar to cold.

Should it be working in this way? Also the plastic 22mm pipe on the cold inlet to the pump is slightly bent not sure if this would have an impact?