OT- Plumbing help!
Turbo Mini Forums

Got a boiler that heats both the hot water and the central heating. it heat the water and sticks in the hot water tank. The boiler is downstairs..

It has 2 big cold tanks that i assume are used for the hot water feed in the roof.

just lately its managed to overflow the tanks in the roof. even though i've tied the ball-cock up so its not being filled that way. it also warms the water in those tanks.

Next to the hot water tank is a pump and some sort of valve. Now i'm thinking its the valve thingy thats goosed but i dont really know and i cant see it being a cheap thing to change just for the sake of it.

I'm stuck now with no hot water and no heating...

Its done it a couple of times before but be switching it off for a few hours its usually sorted. Also there is a plastic lever on the valve thing that i know i've moved before, but now it seems fast and not wanting to move.

Probably no help to anyone but if anyone has any idea that would be great, going to try the plumber in the morning

Cheers
Iain

I've just read up that the problem could be a dodgy mixer tap, if there is a leak between them when the water is off the cold water pressure forces the hot back up to the tank!

Does kind of make sense, problem is finding out which fucker it might be!

There are two seperate systems, one is the central heating circuit, this passes water through a heating coil in the hot water tank (to heat the water in the tank, which is seperate) and then off through the radiators, and back to the boiler. This is a pumped system.

The valve you are on about is known as the 3 way valve. This directs the hot water coming from the boiler either just to the radiators, just to the heating coil in the hot water tank, or to both. This has a stepper motor in it that can be wired to allow the boiler to fire up when it is has made a limit switch. They usually have a manual override lever to place the valve in mid position to give you both hot water and heating.

The two tanks are header tanks, one is for your domestic hot water supply and keeps the hot water tank full, and also feeds the water to your taps by gravity.
Obviously as you turn on the tap, this tank is kept full.
The other tank is for the sealed system, e.g. rads and coil in the cylinder, and the water that passes thru the boiler. This will not often use any water.

The system will usually have an overflow pipe from the sealed system up and into the top of the header tanks. If this water has been getting hot it suggests for some reason that the sealed system has been overflowing back to the header tank.
Not sure on why this would happen, is the pump running? If not perhaps the water being heated by the boiler could expand enough to get back to the header tank?
Or possibly if the coil inside the hot water cyl is u/s then the two systems could be mxing.


I'm no expert at all on the subject, I had to teach myself about how it all worked about 18 months ago when I realised the cunt I bought my house off had made an absolute bollocks of the c/heating system control wiring, I also had to change the 3 way valve, and the pump, they are not horrendously expensive by the way if you do have to replace them.

As for your mixer taps, easy way to eliminate is to go and buy a pipe slice and a load of ball service valves, then turn off mains cold water and fit one in line to each of the taps, easy to do and also potentially useful in future. Then isolate them all, and work round one at a time to see if this solves anything.

This could make sense, as usually the hot water header tank is higher than the sealed header, and the h/w header overflows into the sealed header....

yeah i have service valves in every bit i've done, not the old stuff with the house mind and its something i can do.

Now from what i can see at the minute, the two cold tanks in the roof are interlinked and only 1 has any pipes going in or out. i've not figured where they all go just yet. that manual bit of the 3 way valve wont move at all, so i'm wondering if that has something to do with it. i seem to remember moving it before when i had a problem and it then went away.

Some how though, water is being pushed into the cold header tank as i say, the ball valve isnt leaking and is currently isolated.

Its done it 2 or 3 times before as i said and by switching everything off and letting it all cool down its stopped it. at worst its done it every 6 months which pushes me away from the boiler coil as that would be permanent.

My favourite is a sticky valve of some sort thats finally given up the ghost or a dodgy tap, just need to get my head round it with some light tomorrow.

So what cold feeds are there into the system? Just the header tank ball valve?

If so the system is gaining water from somewhere so it points more towards a dodgy mixer tap.

i need a P&ID drawing

Cold feeds are just into the header tanks yes, my system has two ballcocks, one in each tank.

Hi,
If it's blowing hot water out of the over flows into the header tanks the water is geting too hot causing rapid expansion.
Causes:
Boiler stat
Blockage eg a blocked 3 way (Y plan?) valve, blockages in pipework
Worn pump eg not circulating the water fast enough.
Cheers,
Gavin :)

Edited by Bat on 20th Oct, 2007.

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

I have seen the same thing in my old house. I had the mixer tap shower on, but I had the cold water tap open too much. So the cold water was coming out of the shower head but also going up the hot water pipe into the cylinder and hence the header tank. It overflowed very badly.

How badly is it overflowing? Is it coming out like a tap has been left on or just dripping?

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

like a tap mate. to be honest i'm thinking it may be the new mixer thats been fitted in the bathroom, it uses 15mm cold feed and 22mm hot, wondering if there is a pressure mis-match, just turned the hot side off to see what happens.
It was just after using it to fill the bath that it started happening so its maybe an option.

Bat,
its not blowing hot water out of the overflow, its blowing it into the bottom of the tank, i.e. out an inlet.

Thats why i'm going along the lines of a mixer.

If it is that probem its easy enough to stick a non-return valve in and job done

Hi,
Dead cert mixer tap then.
If you've fitted an inline isolator valve on the cold side to the mixer you could use that to reduce the cold pressure.
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

its got one mate, but when i turned the hot off i noticed that the hot one wasnt fully open, maybe knocked as its a 22mm with a big handle on it.

To be honest i'd prefer to put a one way valve in, then you know you have no problems .

The pressure has always been low on this particular mixer comapred to the rest, (its a combined shower and bath filler fitted remotely in the wall) and now it kind of makes sense.

Anyway, lets see what the test does!

the more i think about it, the more i think thats the problem.

Bloody mixers!

Apparently the only other issue could be a dodgy heating coi, but as i say, i dont think it would of came and went over the months if it was.

well the system has been on a few houts now with that valve isolated and not water pissing out...

Looks like i may have found the culprit but we'll just have to give it some time to find out with it isolated. i only use that mixer about every 2 months so its no great loss!