Glow worm Swiftflow losing pressure fast

[Steth]

Hi All

We have a Glow Worm Swiftflow which has always slowly lost pressure and I assumed this was normal. Over the last few months it's come down to every few days and now loses pressure within hours.

It is regularly serviced and the chap who came out last week fitted a new ? air vent valve in case that was the problem. Nothing has changed.

There is nothing dripping inside the boiler and nothing from the pipe which vents it to the outside. Rads are all skirting rads with no vents, pipes run under a floating chipboard on jablite on concrete floor, so no easy access, but no obvious signs of damp anywhere.

Does anybody have any idea what might be going on, and how we can prove it before we go hacking up random floors unnecessarily?

Steth

 

[Softus]

You've already proved it!

If there's no visible leak, then it's invisible, i.e. hidden, which can mean only one thing - pipework under the ground floor flooring.

How many rooms do you have? Is one of them any more humid that the rest?

 

[Steth]

You've already proved it!

If there's no visible leak, then it's invisible, i.e. hidden, which can mean only one thing - pipework under the ground floor flooring.

How many rooms do you have? Is one of them any more humid that the rest?

There are 8 rooms, none any more humid than the rest

Is there anyway of perhaps disconnecting individaul rads and doing some sort of pressure testing on individual runs?. I suppose I'd need to know the layout of the pipes to be able to make sense of it though

Steth

 

[JohnD]

look for something like this

 

[Softus]

Is there anyway of perhaps disconnecting individaul rads and doing some sort of pressure testing on individual runs?

No way - radiators are plumbed in parallel, not in series, so without going under the floor there's no way to isolate any segment of the pipework.

 

[Steth]

This morning, the thing loses pressure within an hour!! Still no sign of a leak anywhere.

Is there really no possibilty that something inside the boiler could be leaking invisibly between different parts of the system?

Could I pergaps isolate the rads from the boiler and then see if it still loses pressure? Would this then prove it was a leak under the floor or within the boiler?

Steth

 

[gasgeezer]

You could isolate the flow and return on the boiler if no pressure loss then a leak is system side.Warning though if you so much as look at those valves they tend to start leaking

 

[Softus]

This morning, the thing loses pressure within an hour!! Still no sign of a leak anywhere.

I really do sympathise, but I still think you're gonna be lifting flooring sooner or later.

Is there really no possibilty that something inside the boiler could be leaking invisibly between different parts of the system?

Well, so as not to dismiss the idea out of hand...

What you're suggesting is that pressure is being lost from the pressurised heating circuit, which would have been at less than mains pressure when it was filled, into the domestic hot water circuit.

If this is happening then pressure would be lost only when you open a hot tap. Is that its failure mode?

If not, then your postulate doesn't hold water twisted.

Could I pergaps isolate the rads from the boiler and then see if it still loses pressure? Would this then prove it was a leak under the floor or within the boiler?

You could, but you'd need to prove that those isolating valves aren't leaking, or the result will be inconclusive.

To make the job of locating an underfloor leak quicker, there are companies who have thermal imaging equipment, so if the system was running the leak would reveal itself as a hot spot.

 

[Steth]

Isolated the rads, pressure still lost, so definitely no need to lift the floor, thank goodness. (And yes, as predicted, one of the valve is now weeping. Didn't think to check if the loss occurred when somebody opened a tap. Will try that next...

Thanks for the advice so far.

 

[Softus]

Isolated the rads, pressure still lost, so definitely no need to lift the floor...

Erm, did I miss something? Have you checked to see whether or not those isolating valves are "passing", as in not shutting off?

 

[meldrew's_mate]

...What you're suggesting is that pressure is being lost from the pressurised heating circuit, which would have been at less than mains pressure when it was filled, into the domestic hot water circuit...

Surely if the leak was between heating and DHW circuits the pressure would rise to that of the mains rather than drop.

Remember, the failure mode has changed from slow loss of pressure to rapid loss, with no obvious damp problems.


Steth, double check the safety discharge pipework has not been dripping. Set the pressure to 1 bar cold and turn on the heating. Does the pressure rise quickly to over 3 bar when hot? A strong sign that the expansion vessel has lost its gas charge.

Top-up the pressure to 1 bar at night with the system cold. Does the pressure drop overnight? (check before the system heats again).
How quickly does the system pressure risewhen refilling? Less than 5 seconds to refill?

And finally, the constant topping-up over a chronic period will have caused sludge formation in your system, the new auto air vent could have quickly succumbed to the same fate as the old one and be leaking into the boiler casing - combine this with a faulty expansion vessel and it is quite possible your leak has gone out of the flue as steam.

 

[Softus]

...What you're suggesting is that pressure is being lost from the pressurised heating circuit, which would have been at less than mains pressure when it was filled, into the domestic hot water circuit...

Surely if the leak was between heating and DHW circuits the pressure would rise to that of the mains rather than drop.

That's a logical assumption, and the nub of the point that I was making.