I have an ongoing problem with my heating and hot water system which uses a conventional Worcester boiler (not combi) with hot water cylinder and header tank in the loft of our bungalow.

Following my previous post I have reduced the pump setting to avoid pumping over on the heating side but I still have serious air in the rads and have to bleed some of them every week.

What's odd is that the hot water also has air in the pipes which leads me to suspect the hot cylinder as this is the only obvious place where the heating circuit and hot water supply meet.

Because a replacement cylinder is so expensive I don't want to change it unless I'm sure that's the problem but how can I check.

John.

The only way I would think is to pressure test your pipework. Either hire a plumber or pressure tester and do it yourself

Firstly where is the pump located? not in the loft is it?

Mr Whippy

No, the pump is in a kitchen cupboard just below the wall hung boiler.

The hot water cylinder is in the loft adjacent to the cold and header tanks but all these are all some distance (probably 25 ft or so) from the boiler location so the vent pipes etc have a fairly tortuous route up into the loft space and then across to the other side of the bungalow.

you would see your hot water
colour change as the heating water would be leaking into the cylinder
very unlikely as the heating coil is
quite thick wall pipe
but hey im no expert just an enthusiastic
amatuer

It sound more like you have pipes that run uphill. Check that the pipe to the tank heater coil is not sloping down to it's feed, it only needs to be a couple of degrees off level to cause problems and the vent pipe should be straight off this to your header tank. Also check the level in your header tank as this can cause you problems with air in radiators.

have you got a purg o matic on the exspantion tank

read this
http://www.inspectapedia.com/heat/AirBleedValves.htm

http://www.diynot.com/forums/viewtopic.php?t=66912

[Edited on 16/12/09 by thunderace]

Rusty coloured smelly hot water
personally i wouldnt have thought a leak in the coil would cause air in the rads as its submerged in water
sounds like a leak elsewhere you havent had new carpets fitted recently have you?
Ray

We had problems with air in rads all the time cured it by turning the boiler stat down as it was at max setting.

mmm is it possible that the water in the pipes is boiling over venting to the header then drawing air back as it cools
Ray

I had the same problem in my last house, the pump was in the 1st floor airing cupboard and I was pretty sure that it was pulling air in from the vent pipe as the pump started up. When I fitted a new boiler I moved the pump downstairs and under the boiler and it did not happen again.

There are some pipework layouts on http://www.pumptool.co.uk/Position.html and details of their pros and cons.

The original layout in my house was none of the above, the pump was in the horizontal leg of an 'H' of piping. The expansion pipe was on the inlet side of the pump and the fill from the header tank on the outlet side.

porous copper perhaps

IF the cylinder is situated in the attic near the storage tanks , I would ensure that the bottom of the storage tank is at least 3 feet higher than the top of the cylinder. Its highly possible that you could be drawing air through the vent.

Shut off the header tank for the hot water cylinder and run off all the hot water.

If it all runs off and stays run off without the Heating Header tank starting to fill then the coil is intact.

Simples