Central heating loosing pressure

2 Mar 2005
Reaction score
United Kingdom
Hi all,

My central heating is leaking somewhere. I have checked all visible
from the cellar pipework, valves; around combi /pressure relive valve etc/
no visible leaks. Pressure is dropping at about ¼ bar per day.
Had a BG engineer to inspect the boiler, he just refilled the expansion
tank. Pressure still dropping.
Therefore I have few questions to you guys hopeing for some advice

1. I added Sentinel Leak Sealant to the system, overdosing it slightly
/60-70litres system – 1 litre of sealant/. Pressure still dropping but slower.
What is the proper way to use the sealant?
Add it circulate for some time and switch the system off
or just add and use heating as normal?
Keep adding the sealant till the leak stops?
Is overdosing likely to damage the combi boiler?

2. The water pressure gauge on the boiler /Worcester Bosh 28Cdi/
shows the CH pressure but the reading fluctuates when domestic water is taken.
Is this normal?
Are those two systems CH and DHW interconnected?
If yes, is it possible for water from one system to leak in to the other?


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