Conventional boiler overflow issue.

[icemancomeths]

Good Morning all, could someone shed some light into why I get the following issue.

I have a 8 year old conventional boiler, there are 2 tanks in the loft which I'd assume are the cold water storage and the feed and expansion tank (whatever that does). Every month one of these tanks spurts water out of the overflow. The problem is I cant seem to replicated it but this is the sequence of events.

At 7am the hot water was on for half a hour.
At 8am I did some washing up using the hot water.
At 4pm I put the bath on with a mix of taps and hand held shower.
At 4.15pm *knock knock* from next door telling me the my overflow is wetting their clothes in the garden :|
At 4.20pm I look at the cold water strorage which is filling back up now but it is no where near the overflow line (So it must be the F&E?). Even when it reaches the line the ball cock does its job and stops the flow.

Does the Cold tank connect to the F&E? Do these tanks have any other type of overflow that I can't see?

I am really sorry for not painting a clear picture but before I can call a plumber I really need to be able to replicate it.

Thanks in advance.

Sam

 

[easyt]

It could well be just the ball valve on either tank. First thing I would do is, when the overflow is running, pop into the loft and see which tank is filling and whether it is from the ball valve. If it is it shouldn't take a plumber more than half an hour to replace with a new one.

My overflow on the cold water cistern drips about twice a year. I run off some hot water and the cistern tops up the immersion tank, or I flush the toilet bringing the level down. Ball valve closes and OK again for another 6 months. I will replace the valve when I put in a new cistern in the near future.

 

[icemancomeths]

The ball valve's have been replaced and the water does not come from there. Do the tanks also fill up from another source or ONLY the ball valve tap?

 

[easyt]

The cold water 'tank' only fills from the ball valve from incoming main supply. The F&E 'tank' also fills the same way. It is there to make up any water loss in the heating system. The F&E tank also has (in a vented hot water cylinder set up) an expansion pipe leading up from the hot water cylinder and ending above the F&E tank. Normally I think you might get an odd drip entering this tank from condensed water vapour produced when the hot water cistern is heated. If there is a problem with the water heating system then you could get excess water entering via this pipe. I am sure one of the plumbers on here will be able to give better info than me though regarding the other possibilities and how to check .

How often does this event occur. Is it daily, weekly? Do you heat water with electric immersion heater or the heating boiler ?

 

[kay-jay]

no the f+e tank is feed and expansion.
it feeds water into the system and provides room for expansion.
if its not a ball valve problem then its an expansion problem. because its only an issue when you use the hot water i would suggest the likely cause to be a faulty cylinder thermostat. it will not be cutting out when it achieves the set temp and heats till it boils, water volume expands 10 percent in volume as it heats to 100 degrees and 1600 times as it turns to steam. the extra volume needs somewhere to go....the f+e tank ....thats what its there for


KJ

 

[icemancomeths]

Thanks easyt. Its a heating boiler but I think there is a switch for electric aswell (which I have never used). Its probably happend twice in the last month now so its not a daily thing.

Question: Would the F&E tank even be effected 8 hours after the boiler has turned off but I then used the hot water from the storage?

 

[easyt]

Thanks easyt. Its a heating boiler but I think there is a switch for electric aswell (which I have never used). Its probably happend twice in the last month now so its not a daily thing.

Question: Would the F&E tank even be effected 8 hours after the boiler has turned off but I then used the hot water from the storage?

I can't see how the F&E tank would be affected after the heating has been off for 8 hours. See reply above from Kay-Jay. I would still suspect the ballcock if it is happening when the heating system has been off. Particularly if it ia as infrequent as you say. I suspect that in my case it starts when mains pressure is a little higher than usual or that there is a bit of muck under the valve seat.

 

[kay-jay]

from your original post it seems that it happens just after you use the hot water. if so it is more likely to be a cylinder stat than anything else.
turn your stat down to about 40 degrees and run your hot water for a few minutes till the surface of the cylinder feels coolish then wait for it to heat up if it gets hot to the touch beyond 40 degrees then you know for sure its the thermostat

KJ

 

[icemancomeths]

from your original post it seems that it happens just after you use the hot water. if so it is more likely to be a cylinder stat than anything else.
turn your stat down to about 40 degrees and run your hot water for a few minutes till the surface of the cylinder feels coolish then wait for it to heat up if it gets hot to the touch beyond 40 degrees then you know for sure its the thermostat

KJ

Thanks Kay-jay, but would this still be the case if the hot water has NOT been on for 8 hours, I have only run the hot water taps? (Why would it get hotter).

Thanks for your time all.

 

[easyt]

At 4pm he runs the bath. Has your hot water heating not been on in the afternoon as well as in the morning?

 

[icemancomeths]

At 4pm he runs the bath. Has your hot water heating not been on in the afternoon as well as in the morning?

Nope- its not been on since 8am! for some more background, I was washing the dog haha

 

[easyt]

Thought water might have been a bit cool for a bath !!

My money is definitely on the ball valve. Do you know which overflow is running. Could it be the main storange rather than F&E ? I would think it most likely. As I said, in my case when I get the occasional overflow run then running water off allows the valve to reseat and problem solved for 6 months.The fact that you went into the loft immediatly after the overflow problem and the tank was refilling... mmmm. Did the problem then clear? Nothing had been happening with the F&E tank. To my mind if that is the case then I suspect the main cistern ballcock.

Running the bath probably allowed it to reseat.

 

[icemancomeths]

easyt:
The fact that you went into the loft immediatly after the overflow problem and the tank was refilling... mmmm
Thats exactly what I thought, the water level was a good 4 inches below the overflow which made me scratch my head and point to the F&E. If im honest the F&E tank dosnt look that fresh to say a good few gallons of water should've gone through it.

Maybe its just one of those things...

 

[icemancomeths]

Ok:

Using the hot water lowered the water level in the cold water storage tank. If when filling back up it didnt shut off- THIS DOES NOT explain why the level was 4 inches below the level, surly it should be at the overflow level because the hot water was not turned off so the water could only go out of the overflow??? OR does water from the cold water storage go somewhere else for a bit even if the taps are turned off?

 

[easyt]

I reckon, neighbour sees overflow, Iceman starts washing dog, reduces tank level, overflow stops whilst neighbour is coming round. Iceman checks tank, level down after bath/shower on dog. How can it overflow when level down ?? It wasn't it had stopped overflow by time neighbour came round. If happens regularly on new valve maybe some muck or pressure high for valve?

 

[icemancomeths]

easyt:

overflow stops whilst neighbour is coming round

It was definately p*ssing out like a river for a good 20 minutes after neighbour came round (Girlfriend was watching it). I then stopped the flow of water manually (with a broom to keep the ball cock up) then it stopped overflowing (coincidence i guess) which is why it points me to the F&E little tank.

 

[kay-jay]

is the water pi33ing out cold or warm? if its cold it will be the ball valve but it shouldn't pi33 out just trickle out at the same rate as the tank fills via the valve.
if its warm then its your thermostat.

go up in loft shout to mrs to turn on hot and cold taps wait till visible water level drop in both cisterns yell for her to turn taps off and both cisterns will fill up. observe what happens and report back

KJ

 

[kay-jay]

what height is the overflow pipe as it exits the house? what height is the boiler? it could be a valve on the boiler blowing off.

KJ

 

[icemancomeths]

is the water pi33ing out cold or warm? if its cold it will be the ball valve but it shouldn't pi33 out just trickle out at the same rate as the tank fills via the valve.
if its warm then its your thermostat.

go up in loft shout to mrs to turn on hot and cold taps wait till visible water level drop in both cisterns yell for her to turn taps off and both cisterns will fill up. observe what happens and report back

KJ

It wasnt a trickle.

Was it warm or cold? Don't no

Sorry but why the cold tap as well, how would this effect it?

I will report back later

 

[icemancomeths]

what height is the overflow pipe as it exits the house? what height is the boiler? it could be a valve on the boiler blowing off.

KJ

The overflow is in the loft of a 3 storey house, the boiler is in the kitchen bottom floor and the heater tank is on the middle floor. Its like the diagram on page 2 here:
http://www.homebase.co.uk/wcsstore/homebase/assets/ht_understand_cenheating.pdf

 

[helpsy]

Water expands 4% from 4 degrees to 100 degrees,not 10%.

 

[icemancomeths]

It wasnt a trickle.

Was it warm or cold? Don't no

Sorry but why the cold tap as well, how would this effect it?

I will report back later

Sorry but why the cold tap as well, how would this effect it?

 

[kay-jay]

you say you have 2 cisterns in loft one of which is your cold storage, if its a ball valve problem on the cold you need to run the cold till the water level drops then observe as it fills to see if this ball valve is passing. will help to know which tank is causing the problem! i suggested running the taps on both so you could observe both tanks as they fill at the same time

helpsy - yeah i know i confused it with freezing expansion...bit hungover this morning lol

KJ

 

[dontknowitall]

Kay-jay? Do you want me to hold that basin for you while you run out to the van for a couple of fixings? You've been stood like that for weeks now ...

 

[kay-jay]

DKIA - you should know by now that peeing in a basin is an important part of the commissioning process and shouldn't be rushed

KJ

 

[icemancomeths]

Reight then, I have solved the problem and it was simply pot luck.

The reason it was overflowing was because when I ran the taps, water flowed into the cold water tank through the codensation pipe not the valve. This only happens when BOTH bath taps are run on FULL.
So it seems the pressure from the cold water tap is much stronger than the hot water tap and forces it up to the cold water tank. Crazy.

Does this mean the tap is knackered? I have turned the stopcock half closed to release the water pressure and this helps.

Problem: The water level drops below the overflow level but it seems to continue to SUCK the water out of the overflow and the level remains at the bottom of the 90 degree pipe.

 

[helpsy]

Non return valves?

 

[icemancomeths]

Non return valves?

I doubt it has them, its a right bast*rd to get to the pipes though.

 

[kay-jay]

stick it anywhere, water dont compress. airing cupboard will do

KJ

 

[icemancomeths]

Is it safe to let it only flow in one direct?

 

[kay-jay]

right then
firstly your taps are not knackered, its just uneven pressure supplies. from what you say it must be a mixer tap.

fitting a non-return valve (check valve) is the way to remedy this problem. it needs to be fitted anywhere on the hot (weaker pressure) distribution pipework. because as i said before water does not compress. so it can go under the sink in question or it can go on pipework under floorboards (make sure its easily accessible tho) basically any position between the sink in question and the airing cupboard.

if you decide to put it in the airing cupboard....what you should see is a pipe leaving the top of the cylinder vertically then turning 90degrees onto the horizontal then a tee piece one axis horizontal this is the hot water distribution pipe and you can fit the valve on here. the vertical axis from the tee piece is the vent pipe which goes up to the cistern which is overflowing. as the vent pipe is a vital component of the hot water cylinder safety by providing somewhere for expanded volume of water to go in the event of a thermostat failure...YOU MUST NOT FIT A NON_RETURN VALVE HERE there must be an unimpeded route from the cylinder to the cistern.

if your pipework sounds a little different its ok, just probably an old installation, just make sure that the route to cistern is clear and fit the valve on any of the hot distribution pipework.

close to the cylinder is a good bet as it will allow you to add additional mixer taps to other sinks without additional check valves because it provides a non-return route for everything downstream, whereas if you fit the valve below the sink in question and add mixer taps to another sink you will need an additional valve as this problem will re-occur.


hope this clarifies things


KJ

 

[icemancomeths]

right then
firstly your taps are not knackered, its just uneven pressure supplies. from what you say it must be a mixer tap.

fitting a non-return valve (check valve) is the way to remedy this problem. it needs to be fitted anywhere on the hot (weaker pressure) distribution pipework. because as i said before water does not compress. so it can go under the sink in question or it can go on pipework under floorboards (make sure its easily accessible tho) basically any position between the sink in question and the airing cupboard.

if you decide to put it in the airing cupboard....what you should see is a pipe leaving the top of the cylinder vertically then turning 90degrees onto the horizontal then a tee piece one axis horizontal this is the hot water distribution pipe and you can fit the valve on here. the vertical axis from the tee piece is the vent pipe which goes up to the cistern which is overflowing. as the vent pipe is a vital component of the hot water cylinder safety by providing somewhere for expanded volume of water to go in the event of a thermostat failure...YOU MUST NOT FIT A NON_RETURN VALVE HERE there must be an unimpeded route from the cylinder to the cistern.

if your pipework sounds a little different its ok, just probably an old installation, just make sure that the route to cistern is clear and fit the valve on any of the hot distribution pipework.

close to the cylinder is a good bet as it will allow you to add additional mixer taps to other sinks without additional check valves because it provides a non-return route for everything downstream, whereas if you fit the valve below the sink in question and add mixer taps to another sink you will need an additional valve as this problem will re-occur.


hope this clarifies things


KJ

Perfect and thank you, appreciated

 

[stevetheplumber]

have you had any taps changed recently especially in th kitchen ? a lot of modern mixers are not bi flow and will back fill the tank via mains from tap going up the hot pipe