Heating Water only causes rushing sounds from pump.

[Markone]

Hi all,
Can anyone give me some advice as to why when I switch central heating to water only in summer, it doesn't take long for the sounds of rushing water in and around the circulation pump inside the airing cupboard. If I call for radiator heating and the 3 way valve goes to mid position, all goes quiet with the system. The pump is an old WSP GOLD fitted in 1996 (year of house build) and this when circulating the full system is fairly quiet apart from a bit of humming heard.
I have recently cleared a blockage from F&E tank in loft which was the 15mm feed pipe to the heating system. I have also circulated FERNOX DS40 for a week and cleared a lot of sludge from the system. All radiators now heat up well, however, when calling for hot water only and 3 way valve closes to the radiators, the noise is loud and annoying. It feels like it might be damaging the pump running like this. Does any have any solutions to water only heating (quietly) Thanks in advance.

Mark

 

[Aquarius]

Hi Mark, are there any vertical pipes on the pipework to the hot water side of cylinder?

 

[Markone]

Hi Mark, are there any vertical pipes on the pipework to the hot water side of cylinder?

Hi there, thanks for responding... Yes from the 3 way valve 22mm pipe runs about 18" horizontal, then a sweeping bend upwards to the vertical for 24" before it enters the cylinder.

Thanks.. Mark

 

[Aquarius]

Hi there, thanks for responding... Yes from the 3 way valve 22mm pipe runs about 18" horizontal, then a sweeping bend upwards to the vertical for 24" before it enters the cylinder.

Thanks.. Mark

Check for an air vent located at the top of that pipe work, it might just be trapped air. It should look something similar to this:

Slightly unscrew to release any air, keeping a cloth/paper towel for any water. If all you get is water, this may not be your issue.