Manual pump to suck air bubbles out of tap?

Certainly is, Hose pipe if you have two pillar taps.. Cut a loop off it big enough to sit between both taps. Warm the two ends and jam them onto the spouts good.. Hold tight and turn both taps on letting cold pressure blow out the air lock in the hot pipeline up the vent.
Or if it’s mixer wrap something tight, or your hand over the spout and force back up the mixer to do the same.

But you have think about why it keeps air locking?
Have you by any chance got a shower pump connected onto your hot water tank? And if so did the plumber put a Surrey/Essex flange on the top to help air dispersal and did he increase the size of the C/W storage? If not you are going to get this issue a lot on long shower usage as you will bleed the tanks dry…. fast

Thanks, will try that, although as I say, we are not on mains so I suspect same pressure in hot and cold.
The bubbling sounds like it's in the hot down pipe from the immersion cylinder. Have attached a diagram of our system, though please note it does not show our shower over the bath. which takes feed from both hot and cold into a thermostat valve.
Thanks again for your response.
Paddy

Thanks Alan. Any hot tap. I think the problem might be right above the hot cylinder, where the cold feeds into the base of the cylinder but also goes onto the cold taps. If the cylinder feed is restricted due to airlock it could restrict hot feed, even to the point of stopping it altogether? I find that if I run the bath cold tap fast it gets the hot spluttering, then running again.

You are starving the hot because of the filter on the gravity feed from the cold tank.
The filter should be on the mains water feed to the cold water tank and not after it.

There should be a dedicated 22mm pipe from the bottom of the cold tank to the bottom of the hot water cylinder so there as little head loss as possible. To make things even worse the cold water is shared with the direct feed of cold to the taps.

When you first turn on the taps the flow should be ok as its taking hot water in the vent pippe which has already got past the hot water cylinder but as soon as the level of water in the vent pipe is lost the only thing that the hot pipe can do is draw air. Some water will get through the cylinder so you will have a mixture of air and water at the taps.

Put the filter on the mains feed and install a new pipe from the bottom of the cold tank to the bottom of the hot water cylinder.

Alan, thanks for taking the time and trouble to check over my pipework drawing, very kind of you. I'm sure you are exactly right, and so the trouble is starvation and not airlock! So I can safely assume suction will not solve the problem.
We had a new borehole (flowing artesian) drilled last year, and the drillers and water testing lab both advised fitting the necessary u/v and filter after the attic tank, "in case something starts brewing up there" !
So you have identified a solution, and I guess since we don't drink the hot water there is little risk.
Thanks again for your help and advice, very much appreciated.
Paddy

paddyinwales said:

Alan, thanks for taking the time and trouble to check over my pipework drawing, very kind of you. I'm sure you are exactly right, and so the trouble is starvation and not airlock! So I can safely assume suction will not solve the problem.
We had a new borehole (flowing artesian) drilled last year, and the drillers and water testing lab both advised fitting the necessary u/v and filter after the attic tank, "in case something starts brewing up there" !
So you have identified a solution, and I guess since we don't drink the hot water there is little risk.
Thanks again for your help and advice, very much appreciated.
Paddy

Click to expand...

Set the hot water cylinder to 60 deg c and that should kill anything nasty but I really do not think it will be a problem anyway.
I have been dealing with ShowerPowerBoosters customers since 2012 and I have had lots of jobs where customers with borehole water put in UV and filtration but they always do this before the break tank. Spotting your plumbing did not do this was therefore easy. You can improve the water pressure and water flows in your home with one of my pumps but only if you think that is a problem.