Water Discharge

[tbrain]

I've got a Glowworm Flexicom 30sx boiler & a Santon premier plus 170 unvented hot water cylinder with seperate expansion vessel. The PRV outlet from the Santon hot water cylinder uses the same copper pipe outlet as the boilers safety discharge.

It seems to be discharging around probably 500ml of water every 24 hours via the safety discharge outlet (to be clear, not the condensate). If I turn on the central heating & hot water seperately, there is still discharge i.e. I can't isolate it to either the central heating system / boiler or hot water cylinder.

The temperature of the central heating system on the boiler shows as 66 degrees.

Any guidance as to why this may be happening?

 

[ianmcd]

well first of all they are not installed properly they should both have individual releif pipes not share one and the unvented cylinder should have a tundish installed so you could see the water dripping if it was coming from there, try undoing the nuts at the individual PRVs and see which one is dripping

 

[tbrain]

Thanks for the reply.

After closer inspection, the unvented cylinder does have a tundish installed & it doesn't drip so I guess that we've isolated the problem to the boiler.

Any ideas? Could the boiler PRV need replacing or is it something simple like a seal?

 

[tbrain]

Could air in the system cause this discharge? Does the seal need replacing on PRV?

 

[Agile]

If the water was coming from the boiler then you would be topping that up daily.

Its almost certainly coming from the unvented cylinder. It will come out when reheating from cold.

The problem is probably caused by a non working expansion vessel. When was the cylinder last serviced?

Tony

 

[tbrain]

"Its almost certainly coming from the unvented cylinder. It will come out when reheating from cold"

Even though it leaks when only the central heating is on, and the hot water off?

"The problem is probably caused by a non working expansion vessel. When was the cylinder last serviced?"

Never. Been in about 2 years. The boiler is annually serviced by Glow Worm. The unvented cylinder is a Santon. I'm guessing that this should be serviced asap? There is a seperate expansion vessel sitting above the unvented cylinder. I'm assuming that you mean this and not the boilers inbuilt expansion vessel? I had ruled the seperate expansion vessel out as I had assumed that if the problem that it would see water dripping via the tundish on the unvented cylinder?

 

[Agile]

What is the boiler pressure showing?

Is the filling valve firmly off?

The water has to come from somewhere! Its either the cylinder or the boiler!

IF the boiler is correct then it can only come from the cylinder! In that case it will be throught the tun dish!

You could temporarily disconnect the boiler PRV vent ( and ideally take it to a seperate discharge point ).

I can only assess your problem based on what you are telling us.

Tony

 

[Charnwood]

If nothing is visible passing through the tundish then it is the boiler.

If the boiler is working then that 500ml is coming from somewhere. The PRV will open at (probably) 3 bar, normal working pressure should be roughly 1.5 bar.
As Agile asked, is the fill-valve letting by?

 

[tbrain]

Boiler pressure remains constant at 1.0 bar, filling valve is definitely closed / off.

I've just asked the other half to stick the heating on for a couple of hours (I'm not at home until later), and no discharge. So, like you say it must come from the cylinder (both central heating & hot water must've been on when I ran this previously). Just a bit confused as when I ran this test previously, there was no discharge via the tun dish. However, I'll have another look later, and re-run these tests to be sure.

If there is still no evidence of discharge via the tun dish, I will disconnect the boiler PRV like you say and re-run just to double check no discharge from boiler.

This should then tell me who I need to get in to solve the problem i.e. Glow Worm for boiler & annual service, or A.N Other to look at cylinder / expansion vessel (Santon via Baxi who provide their servicing, or maybe just my original plumber!?)

In your opinion, if the expansion vessel is the problem would it be kaput or is it salvageable? Could it have depressurised? If so, I'm guessing that checking this & attempting to repressurise would be an obvious first port of call & also check whether the diaphragm is kaput (or should I leave this to the experts!?)

Thanks for your help, much appreciated!

 

[CBF]

you need someone with a G3 cert to service your cylinder which BTW should be done on a yearly basis for safety & to maintain the warrenty

 

[tbrain]

you need someone with a G3 cert to service your cylinder which BTW should be done on a yearly basis for safety & to maintain the warrenty

Ok, sounds like this needs doing anyway so will give my plumber a ring (he has a G3 certificate)...

 

[Agile]

The air pressure should be checked when the cylinder is installed!

For it to fail so soon makes me worry that he did not set it correctly.

You could ask him if he checked/set it at installation!

Remember it only discharges when heating up from cold! To see it in the tundish you may need to prevent it reheating until you are ready to watch it!

Tony

 

[tbrain]

Ok, it sounds like it would be worth calling him in to have a look...

Yeah, understand the fact that it only discharges when heating up from cold! The hot water is programmed to come on twice a day, early morning & evening. I will monitor it tonight when it comes on.

Thanks!

 

[Agile]

Unless you have used a lot of water during the day there may not be much heating to be done!

Tony

 

[tbrain]

Ok, I advanced the hot water last night, and as suggested there was a clear drip into the tundish from the cylinder!

Next step is to check the pressure of the aquasystem expansion vessel this evening. I'm borrowing a gauge to do this & will let you know the outcome...