Unvented System - Cold Water Discharge

[Dreadnought]

Hello.

Just moved into a new house - water/heating was not working so I got it serviced and now is up and running.

Once the guy had gone, I see I get a (small) dripping discharge of cold water from the discharge pipe.
Water is always cold.

When hot water is not being heated, it stops dripping.

I phoned the company who did the service and the guy who did it said "You need a new unvented cylinder, we can give you a quote".

The cylinder is an Oso (bubble) - he said it is probably losing pressure all the time.

But I simply could not get an explanation from him to demonstrate his logic or reasoning. All he wants is to replace the cylinder (£££).

Clearly there are a number of faults that will give rise to venting of cold-water and all I want is a reasoned argument as to why is *must* be the cylinder !

Advice please.

 

[Ch4 plumbing]

Did they say new unvented cylinder or new expansion vessel?

 

[Gray0689]

Get someone else in to look could be simple as a TPRV worn
Or an external expansion vessel may be needed

Wouldn't just jump in to saying need new cylinder

 

[SJB]

It's a bubble top cylinder so the bubble has most likely gone.

You need a G3 qualified plumber to come look to be sure tho as if it's not the bubble then it's a problem with one of the safety controls and can't be touched by anyone without a proper ticket.

 

[Dotty]

Job 38.11