Expansion tank overflow now that new condensing boiler has been fitted.

[WickedestSound]

Hello.

I've just been reading through this great site and thought I'd post my issue here to see if anyone can help please?

We have an open vented, fully pumped (I could be wrong) central heating / hot water system and just before Christmas our 20+ year old bolier started leaking at the heat exchanger. We called in a friend who has a plumbing business and had the boiler replaced with a GlowWorm condensing boiler. I don't think the old boiler was a condensing one. He also flushed the system with flux and sludge remover, fitted a gold magnetic filter to the return pipe near the boiler and all was well.

After a couple of days we started noticing water outside on the patio. It turns out this has been coming from the feed and expansion tank overflow pipe.

What is now happening is that once the pump shuts off, roughly half a pint of water is coming out of the vent pipe which goes up and then down over the expansion tank. It only happens after the system has run and the pump shuts off. After a while the level in the expansion tank rises enough that it just reaches the overflow and hence the water outside.

The system worked fine before the boiler switch over. Things that have been tried are opening a bypass valve (I'm sorry but not sure what this is) and also turning down the pump from 3 to 2 but the problem still exists.

We are in a bungalow that has had 3 rooms built into what was the loft space. The layout of the system is the boiler on the ground floor with the hot water storage tank above it in the same cupboard, and then upstairs in what's left of the loft we have the cold water storage tank and the feed and expansion tank. 3 radiators upstairs and 7 downstairs.

The heating and hot water works fine, all radiators get fully hot but there's this water from the vent after the pump shuts off. The water is clear and cold.

Sorry to go on a bit but we can't seem to pinpoint what might be causing it.

I know it's hard to comment without actually seeing it but if anyone can offer any advice on this please then I'd be really grateful.

Thanks for reading.

Alex

 

[doitmyself]

Could be the feed pipe from the F&E tank to the boiler flow pipe is blocked.

Lock your motorized valves in the MAN position then drain some water out of the system (drain cock usually on the last radiator) while someone watches the water level in the F&E tank. If the level does not drop and the ball valve open, the pipe is definitely blocked.

If no blockage, let the water cool down and then check how deep the water is in the F&E tank. It should only be about 2 inches above the bottom outlet. You can change this by bending the ball valve arm. Check by draining some water and noting where the ball valve opens. Make sure it is before the water level reaches the outlet.

 

[WickedestSound]

Thanks doitmyself.

I don't think it's a blocked cold feed as he can drain down the system and then fill it up again. We have the heating on at the moment but if memory serves when the system is cold the F&E tank is only 1/3 full and roughly 2 inches above the cold feed outlet.

Any other suggestions please?

Many thanks

Alex

 

[Paulus]

I racked my brains over exactly the same problem. One of the guys on here (sorry I can't remember who) finally suggested a new float valve in the f&e tank and was spot on. I cleaned out the tank, fitted a new valve and reduced the amount of water in the tank slightly and have had no problem since.

It may be worth a try. .

 

[doitmyself]

The water level rises when heated up.

Is it a combi boiler (no HW cylinder)? If yes, turn the pump down from 3 to 2.

 

[jtsplumbing]

Can you let us know what model glow-worm boiler has been fitted ? then we may have a better idea what is going on ! eg; hxi / sxi / Flexicom / Betacom but more information on boiler type will be helpfull.
:sleep1:

If it is a combi you should not have a expansion tank (fix`d speed pump you can-not slow it down) :8:

 

[WickedestSound]

OK sorry for the delay getting back. Thanks for all the replies.

It's a Glow-Worm Flexicom 18hx which I think is a condensing boiler. I don't think the old one was a condensing one.

The pump was set to 3 so as suggested I changed it to 2 and while it made the system quieter the water still comes from the vent pipe.

Today I have tied off the float valve and reduced the water level in the expansion tank so that the water level is just 2 inches over the top of the feed pipe. It was about 5 inches before I reduced it.

I ran the system tonight on it's hour program but alas once again once the pump shut off the water came out of the vent pipe.

My plumber's not getting back to me about it either which isn't helping.

Does anyone have any other suggestions please?

Thanks again.

 

[dancinplumba]

did water level still rise ?

 

[WickedestSound]

I actually can't say hand on heart that it did. It looked as though it was higher but I didn't measure the level as I did when I took some out this afternoon. I think it was a bit higher though.

Sorry I can't say for sure...

 

[dancinplumba]

leave ball valve tied up for a while, make 100% sure its not passing/dripping and see if it rises, if it does, could be leak on dhw heating coil, if it doesnt, could be you have too much resistance on heating circuit, does it do it on dhw heating only as well ?

 

[jtsplumbing]

Ok. yes it is a condensing boiler, Heat only, with open vent and hot water cylinder, Do you know what make boiler was removed ?
as it is possable that flow and return pipes have been crossed over on boiler, what is the hight of the expansion tank above the top floor radiators ?

 

[WickedestSound]

It's definitley not dripping/passing water on the float valve. The hot water tank is only a few years old and has the polystyrene insulation already attached to it all over.

The water comes from the vent pipe if it's set to just central heating but also if it's on both hot water/central heating. I don't think we've tried it just on hot water.

Thanks

 

[Simon F]

you say this happens when the pump has turned of, could it be that its the boiler that is of and pump on over run?
do you have a 3 port or 2 x 2port valves

 

[WickedestSound]

JTSPlumbing - The old boiler was a Glow-Worm FuelSaver 35F Fanned Flue Boiler.

The expansion tank is about 1 metre above the floor level on the same floor as the upstairs 3 radiators. So, the bottom of the expansion tank is roughly 50cm above the tops of the 3 radiators.

I hope this helps.

 

[doitmyself]

What is the vertical distance from the pump to the water level in the F/E tank?

What is the vertical distance from the water level to the top of the bend in the vent pipe?

Can you post a pic or drawing showing how the feed and vent pipes connect to the flow from the boiler?

 

[WickedestSound]

Simon F - The timer is set to go off at 6pm which I think turns off the boiler (no water from pipe at 6pm) but as you say the pump seems to carry on which I'm sure it didn't do before. At approx. 6:05 the pump can be heard to shut off and this is when the water comes from the pipe. The water is clear and cold.

I'm so sorry but i'm not sure what you mean about the ports.

Thanks...

 

[jtsplumbing]

See simon f has raised a point, may-be pump is -not wired back to boiler, system stops , boiler still hot, expanding over tank,
as for hight of tank like to see a least 1 Mtr above highest rad.

 

[WickedestSound]

Doitmyself - What is the vertical distance from the pump to the water level in the F/E tank? 2 metres

What is the vertical distance from the water level to the top of the bend in the vent pipe? 30cm

I'm just going to try and get a picture of the feed and vent pipes and how they connect.

Thanks

 

[WickedestSound]

I'm sorry but I can't seem to work out which pipes are the feed and vent! I will have a proper look in the loft tomorrow to see if I can work it out.

Thanks for everyones time this evening, it's much appreciated.

 

[Stuthewarrior]

Maybe the pump has been fitted the wrong side of the filling and vent pipe work
Cheers Stuart

 

[LeakFinder's]

get a local plumber to complete a pressure test on the domestic hot if it holds pressure fine get the heating set up as a pressurised system as it could be purely pumping over. if it fails get the coil on the cylinder bypassed and see if it still occurs. if it stops then likely a perforated coil and needs the cylinder replaced.

 

[doitmyself]

What is the vertical distance from the pump to the water level in the F/E tank?

2 metres

That's good.

What is the vertical distance from the water level to the top of the bend in the vent pipe?

30cm

That's not enough. It needs to be at least 45cm and preferably nearer 60cm.

 

[jtsplumbing]

Has the installer wired the pump back to the new boiler ?? dont think the old fuelsaver had pump overrun !!

 

[rocketmanbkk]

sounds like one pipe circulation to me?

 

[WickedestSound]

Hello again,

After reading the replies here and a bit more research online I am starting to agree that the top bend of the vent pipe is not high enough and therefore the vent pipe cannot retain the surge water when the pump stops.

The F&E tank in our loft is fairly close to the pitched roof. As the vent pipe cannot be extended vertically much higher than it is already can it be raised if it followed one of the rafters up at say 45 degrees (or thereabouts) until it reached 60cm please? And then bend around in a U shape and come back down over the F&E tank please? At the moment it comes up at 45 degrees and just has a right angle bend in it so it then goes down at 45 degrees and sits over the tank.

Also I am attaching a picture of what I believe is the cold feed and vent pipe above the pump as one of you asked to see this. I believe the cold feed is the smaller diameter pipe and the vent pipe is the larger one.

Hope this helps!

Thanks for reading.

 

[WHPES]

Is there an automatic bypass valve fitted? (If not there should be)

I had this problem once - Put your motorised valve(s) to the manually open position (lever on the side and locking lug) and see if the problem still happens then. If not it could be a wiring / electrical issue.

 

[rocketmanbkk]

from the top of the tank where the pipe comes out, the pipe should extend at least 450mm and then the vent pipe should go to the F & E in the loft, any less is no good as you will (may) get one pipe circulation, take a photo of the top of teh tank and post it here, we need to see it, measure it also and tell us how long it goes alsong until the vent is cut in.

 

[WickedestSound]

Thanks rocketmanbkk. OK, here's the pictures of the F&E tank. The first picture shows the F&E tank with the vent pipe over the side. There is only 30cm from the top of the bend to the waterline in the tank. People have said this is too low.

The second picture shows the back of the F&E tank with the vent pipe going down almost 80cm where it comes alongside the cold feed pipe. The third picture shows both the cold feed and vent pipe running next to each other on a downward slope over to the corner of the house (run must be 2.5 - 3m).

The last picture then shows the cold feed and vent pipes comes down through ceiling and then over to meet the rest of the pipework just before the pump.

I hope this helps.

Thanks again...

 

[rocketmanbkk]

OK, but the water vessel in the airing cupboard, the hot water pipe come out the top (?), it should the immediately at 90 degrees branch of, then, at a minimum distance of 450mm the vent pipe should going to the F & E tank, is the 450mm there? If not, water will go back in the water vessel (maybe) but it will also go up the vent pipe as its an easier route, it must extent 450mm minimum before you can cut the vent pipe in.

What is the measurement?

 

[rocketmanbkk]

sorry about my spelling! note to self, remember to spell check!