Strange Dripping Overflow

[techno492]

Hi Guys,

Bit of a strange one here, I noticed a while back that my outside overflow was dripping very slowly when the heating / hotwater was on.

Called the plumbers who installed the system in and they said it was possiablly steam in the header tank traveling down the overflow, condensing and dripping from the pipe.

While the plumber was looking at the header tank we had the system on full blast with the boiler stat on max. The pipe work in the airing cupboard and radiators became very hot. (Room Stat set at about 22 degrees)

He decided that the boiler stat could be at fault and arranged for Ideal to come and look at the boiler. They came out and replaced the Boiler stat. However, the overflow is still dripping.

ive turned the boiler stat down to just above minimum, when the system comes on, everything is a lot cooler than when its on max so im guessing thats elliminated the issue of the boiler stat and the hot temperatures we experacend when the plumber was looking at the header tank was merely because the system was running at max 82 degrees.

The strange thing is that the overflow still drips with the boiler stat turned down.

The water level in the header tank is fine and is a couple of inches below the overflow pipe.

The boiler is running normally and isn't cutting out on an overheat situation.

Does anyone have any idea what could be causing the drip ??

The system is a Megaflo unvented hot water cylinder with a vented heating system heated by a Ideal ICOS HE12 boiler.
The system is not even 2 years old and was put in when the house was built.

If it makes a difference, the only work on the plumbing I have had done is to replace the kitchen sink and tap with a monoblock mixer tap.

 

[techno492]

any ideas anyone ?

 

[Hugh Jaleak]

If you're getting steam then i'd be seriously worried! (And so should your 'plumber'!)

Where does the overflow pipe come from? Is it from the feed and expansion cistern for the heating or the safety discharge on the megaflow?

 

[techno492]

The overflow comes from the Expansion and Feed cistern.

Im not convinced that there is any steam but then I cant think any other reason there would be condensation.

I had the boiler stat down to 40ish degrees today and the overflow still dripped. I checked the pipe work coming from the megaflo and it was no where near as hot as when we have the boiler stat on full so the boiler stat is functional.

The other odd thing is that my neighbours is dripping slightly as well

 

[Hugh Jaleak]

Possible system is overpumping slightly, can you observe the expansion pipe (inverted U discharging back into the F&E cistern) whilst system is operating. This may be pumping water back into the F&E cistern faster than the cold feed can put it back into the system. Another option could be expansion with water level in F&E cistern set too high, but would have expected it to overflow more when system is running at a higher temperature.

Not good for the health of the system, will result in constant topping up with fresh water, and will cause the level in the cistern to rise and overflow. Normal practice would be to set the level in the F&E cistern about 1/3rd full when system cold.

 

[techno492]

Just got in, the heating has been running for about 45 mins and it has let out 1 drip, can't get into the loft but I can't hear any water being put back into the F and E.

 

[plumbplumb]

If the pump is running and the open vent is discharging into the F+E then as stated above the system is pumping over. This could possibly be a result of insufficient head on the pump/pump speed too high or restriction around the cold feed/open vent area or even down to how the system is configured.

This will cause the F+E tank to get warm because heated system water is being pumped into a tank of cold water