Central Heating Over Flow Issue that's stumped many heating engineers :(

southcoastrgi

that roof tank only has one outlet to the cylinder so your cold must be on the mains, so any mixer tap or shower could cause the cylinder to back fill

Ruski

southcoastrgi wrote: »

that roof tank only has one outlet to the cylinder so your cold must be on the mains, so any mixer tap or shower could cause the cylinder to back fill

Good spot Southcoast - problem solved me thinks :D:D

To prove the point just go run your shower and stick your head in the tank (not literally!)
Any other 'mixers' in the house???

Russ

drummer_666

can the water make its way up from the mains pipes entering the house?

because sometimes after the tank has been drained the cold water tank fills up over night

drummer_666

Well left taps on ages in turn.

Bathroom mixer - no water entering tank.
Shower mixer - water entering tank but from what looks like mains feed (pic below - it's left side of the tank)




Also as I was using mixer, isn't water supposed to be going into the tank - to refill?

After I'd ran taps for ages and turned off, the cold water tank was nearly empty so it began refilling (out of same place in pic above)

I turned off the tap on the pipe, so water couldn't enter the cold water tank and then ran shower and no water came out.

Also, the tank fills up without using the shower.

Owain_Moneysaver

Another possibility is that there is an internal leak in the hot water cylinder and water from the boiler primary circuit is getting into the hot water.

The boiler primary circuit losing pressure supports this possibility, although it's unlikely it would cause continual overflow unless the filling loop on the boiler is also letting through.

drummer_666

The cylinder is a year and a half old so wouldn't a problem with it would be unlikely?

My boiler hasn't lost pressure since I topped it up slightly last week either (don't know when was last topped up as I was away 2 months with a lodger here) - if that's the pressure you mean?

I'm going to get a check valve added to the shower mixer and see if this sorts the problem... fingers crossed. If not then will be picking your brains on here yet again

Ruski

Unfortunately you won't 'see' water if it's back pressuring up the hot water pipe - it will enter from the bottom of the tank - so you have to observe the level in the tank. Try to attach a ruler somehow in the tank to give you observable levels.

Did you say this only happens overnight when nothing is being used??

Russ

drummer_666

Hi Russ,

Water flows out of the overflow pipe constantly all day and I presume all night

But if the tank has been emptied. i.e. running hot top for ages which the sole purpose of emptying the tank, it might not overflow again until morning, but then sometimes it does it later that same day

Ruski

Is this not, therefore, just a question of adjusting the ballcock in the header tank then?
When the header tank is 'full' the water level should be about an inch below the overflow outlet. Is that what you observe?
Does the water definately stop running from the ballcock when it reaches 'full' level? Very often a slight drip/run will add sufficient water for it to overflow - not uncommon if the ballcock is not shutting off correctly.

Let us know

Russ

drummer_666

nope, the valve was replaced and ballcock adjusted by my dad. didn't solve problem.

other trades people have tried that first and said it is shutting off ok too

not an inch below but it is below

also noticed something weird earlier - the water had risen after i drained it and water coming out overflow pipe, i drained some water again til it stopped coming out the pipe... looked in tank and the pipe was actually still under water (but no water coming out).

Presume i'm looking at the right pipe cause can only see one