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Tim Cooke
Tim Cooke,
Category: Appliance
Satisfied Customers: 1361
Experience:  Owner at Self-employed
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My Worcester-Bosch boiler is losing water pressure. I top it

Customer Question

my Worcester-Bosch boiler is losing water pressure. I top it up but the pressure keeps going down. there are no leaks on the radiators. The overflow pipe outside has a puddle beneath it
JA: Are you getting any error codes or blinking lights on your boiler? How old is it?
Customer: no blinking lights that I can see. the boiler is 6 years old
JA: How long has this been going on with your boiler? What have you tried so far?
Customer: It has been going on for a couple of months checked radiators for leaks
JA: Anything else we should know to help you best?
Customer: I have a plumber friend who says it could be the pressure relief valve
Submitted: 9 days ago.
Category: Appliance
Expert:  Tim Cooke replied 9 days ago.

Good morning, and welcome to the Technical section in JustAnswer. My name is ***** ***** I will help you today. There's no time pressure on this topic - it will stay open to you for many days, and you can reply at any time. I will be away from my desk sometimes, but will respond as soon as I can.

What is the pressure before you top up, and what it is afterwards? And when the boiler is running, how high does the pressure gauge go?

To help diagnose the problem, you need to tie or tape a polythene bag, like a sandwich bag, over the end of the pressure relief discharge pipe, which on the outside wall behind the boiler. After 24 hours of running the boiler, do you get any water in the bag?

When was the boiler last serviced?

Expert:  Tim Cooke replied 4 days ago.

Good evening, I haven't heard back from you yet.

I've just realised that you had already noticed a puddle underneath the discharge pipe, so there's no need for the bag test.

The next step is to turn off the boiler, drain it, and test the pressure of the EV (expansion vessel). If it's low then you can pump it up, but if it doesn't hold its pressure then it has failed and will need to be replaced. Once that EV is fixed, you can replace the PRV and the discharge will stop.