Low hot water pressure (airlock?)

[jamesih]

Hi,

We have a Glowworm Ultimate boiler with a Y plan central heating/hot water setup.

The hot water pressure is the problem; when we run a bath (at which point the pressure seems fine) and then turn on the hot tap in the same bathroom it starts off fine for a few seconds then turns to a trickle and then nothing. When we then turn the bath off it gushes out of the hot tap.

The same thing seems to happen with the hot taps downstairs.

I have checked the feeder tank which is filling fine and maintains a level of about 3/4 full.

I have ensured any stop cocks are open and I have unscrewed what I believe to be the air vent coming from an upper pipe connected to the hot water tank but just water comes out.

Is it time to connect my washing machine hot/cold together to flush any airlock??

Any further advice?

Many thanks.

James.
James,

 

[Gas2Air]

Have you had any work done to the HW circuit recently? Has the problem only just appeared? How old is the current arrangement?

 

[jamesih]

We have done no work on the HW or CH and it has really been like that since we moved into the house about a year ago - I just would now like consider solving it.

The whole system is about 10 years old.

Thanks.

 

[Gas2Air]

Nothing to do with the boiler. It's an existing fault then. You may have dead legs (old capped off supplies), or uneven pipe run from the cylinder that can cause air pockets, that simply vanish for periods and then come back.

Is it a standard 36"x 18" or bigger/smaller lagged cylinder with a copper pipe existing from the very top?

Assuming your pressure and water flow are ok of course at good times, i'd suggest you have it checked by a plumber.

Have so many customers complain of buying a house and the previous occupier had messed with plumbing/heating etc. Wonders never cease!

 

[jamesih]

The cylinder is larger; is't about 48 x 18 inches but it does have a large copper pipe exiting the top (with others lower down also).

As far as I am aware the previous owner had nothing done and was certainly not a DIY-er.

Would you suggest my description of our problem is symptomatic of an air lock?

As far as I understand it in a gravity fed system there can only be a certain number of reasons why the hot water pressure is low :-

1) Feeder tank not correct level
2) Air lock
3) Valve not open fully
4) Pipe blockage (interesting to locate )

Have I missed anything would you say?

Many thanks for your help so far.

James.