Problem with Glowworm combi boiler?

4 Jun 2007
Reaction score
United Kingdom
My Glowworm Swiftflow 75E requires a new expansion vessel. The existing vessel will not recharge and water comes out the valve. After 10 mins of the central heating being on there is a ticking sound and a sudden rise in pressure and shutdown with banging noises.
I was thinking to install this 8 litre expansion vessel

According to the Glowworm manual the 75E has an 8 litre vessel attached.
The nominal maximum flow temperature setting for central heating is factory set to 82 degrees centergrade.

It's a small 2 bedroom house with 5 radiators. 2 floors.

Is the 8 litre Altecnic Zilmet Expansion Vessel suitable as an alternative?

Sponsored Links
It should be OK as long as it is suitable for a heating system. It looks as if you have other problems, possibly a failed pump or other lack of circulation.

The pump sound like it's operating, could it possibly be a faulty PCB?
I can purchase a PCB on ebay for about £60.

I'm undecided whether to repair the boiler or replace.
Also, after the shut down, if i turn on a hot tap, very hot water flows out without the boiler engaging. After about 20-30 seconds it does engage.
This model doesn't have a diverter valve, instead it has a twin tube heat exchanger. Could there be a leak or faulty valve causing central heating water to enter the domestic hot water system?

Sponsored Links
The expansion vessel arrived this morning so I will install it during the weekend. Will I need to isolate the faulty vessel?
Occasionally the sudden rise in pressure / banging then shutdown doesn't happen. Instead the boiler keeps on running until the radiators get really hot then it just cuts out (pump runs for about 20 seconds after). Is this a thermostat / PCB problem?

Any ideas?


DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local