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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Isolating Valve Problem https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1518043340 Message started by Phil the Fluter on Feb 7^th, 2018, 10:42pm

Title: Isolating Valve Problem
Post by Phil the Fluter on Feb 7^th, 2018, 10:42pm

The filling loop on my combi boiler has a check/isolating valve at one end and an isolating valve at the other (furthest from the cold water feed).

The isolating valve seems to be wide open in the fully-closed position (water will flow through it as if it wasn't there) but, if I turn the lever a little way away from the fully-closed position, the valve closes perfectly.

I'm thinking of giving the l lever a good wiggle to see if I can flush out any impurity that might be preventing it closing properly.

Any comments or suggestions would be gratefully received.

Title: Re: Isolating Valve Problem
Post by thescruff on Feb 8^th, 2018, 11:52am

Likely to be the handle spinning on the shaft.

Title: Re: Isolating Valve Problem
Post by Phil the Fluter on Feb 8^th, 2018, 12:58pm

Thanks for the reply.

As an experiment, I've just removed the plastic handle and tried opening and closing the valve using a pair of pliers on the brass fitting.

The situation is exactly the same no matter whether I use the plastic handle to operate the valve or work directly on the brass fitting.

In the fully open (handle vertically down) position, the valve is fully open and as I rotate the handle clockwise towards the horizontal position, the valve closes fully - as one would expect. However, as the handle reaches the horizontal position, the valve opens again – not fully but quite substantially.

Title: Re: Isolating Valve Problem
Post by thescruff on Feb 9^th, 2018, 1:03am

Sounds about right, it's only a ball with a hole drilled through it, as you say, horizontal is off, the handle should stop it going past horizontal unless it's worn.

Title: Re: Isolating Valve Problem
Post by Phil the Fluter on Feb 9^th, 2018, 10:35am

Sorry, I must've explained the situation badly.

The horizontal position is NOT off: the valve closes fully as the handle approaches the horizontal position but, as it reaches the horizontal position, it opens again – not fully but certainly significantly.

The valve has not been subjected to much used during its lifetime: it's probably only been used a handful of times since the boiler was installed.

Title: Re: Isolating Valve Problem
Post by thescruff on Feb 9^th, 2018, 12:39pm

Not being used adds to the problem as the stick. They are roughly off when the handle is horizontal to the pipe, but you have to allow for ware the same as the old washer type valves that needed re-seating.

Title: Re: Isolating Valve Problem
Post by Phil the Fluter on Feb 24^th, 2018, 12:31am

I've decided to replace the faulty valve described above.

The manual describes the valve as a "stop valve". Is that the same thing as an isolating valve?

The faulty valve certainly looks for all the world like an isolating valve (with a black lever).

The Baxi manual shows the filling loop system thus: DHW mains inlet > stop valve > double check valve > filling loop > stop valve > CH return

The faulty valve is the one attached to the CH return.

Is it simply an isolating valve?

Title: Re: Isolating Valve Problem
Post by thescruff on Feb 25^th, 2018, 9:58am

In this case, they are both the same, although stop valve would be the better terminology.

Title: Re: Isolating Valve Problem
Post by Phil the Fluter on Feb 25^th, 2018, 1:26pm

Thanks for the reassuring reply.

Title: Re: Isolating Valve Problem
Post by Phil the Fluter on Apr 6^th, 2018, 11:52am

Today, I thought I'd have a go at replacing the faulty stop valve on the filling loop.

Having shut off the heating flow, the heating return and the cold water inlet on/off valve, I drained the boiler via the drain off point.

I removed the flexi pipe of the filling loop and opened the faulty stop valve.

A little bit of water came out, then a pause, then a little bit more water, and then another pause, then a bit more water and then a steady flow of water emerged.

Having already drained the boiler via the drain off point, I wasn't at all sure where this "new" water was coming from.

Not wanting to empty the local reservoir (the worst case scenario!), I closed the stop valve and didn't proceed with the operation.

Should I have let this water flow until it stopped flowing, and then proceeded to replace the stop valve?

Advice much appreciated.