wifes been telling me the pipes in the loft have been banging about for a while now, so i thought ‘air in the system, bleed the radiators’. todays my first day at home and heard it for myself. thought id try and work out which pipes were making the noise so i could give a plumber any info if it came to that.

so….. went up into the loft and its steaming!! the pipe that fills the header tank is spewing boiling hot water into the tank!! i was under the impression thats a cold feed that tops up the system from the mains when any waters been used. mrs expunk assures me this happens every day for 10 mins around 7am, and nothings on. no shower, washing machine…..

whats happening? firstly whys it topping it up when nones being used, and secondly whys it scalding hot water??

if its relevant, she also says shower is boiling hot sometimes and she cant make it colder. yet when i try it in the evening its fine. again if its relevant, we have a hot water tank with thermostat which is on a timer for morning water, and we use the timer on the setup near the boiler (this is the ‘central heating and/or hot water’ timer) for the evening water. so its using leccy in morning, gas in evening to heat water.

can anyone diagnose the problem please?

thanks

,, morning.. nice problem to start the day!

the hot water that is filling the tank is coming from the copper pipe that is bent over the top of the tank. its a vent/ expansion pipe that is used when the water in the system is too hot it vents into the tank and the tank replenishes the system.

couple of reasons for this to happen.. a thermostat on the boiler itself is bust and the boiler is literally boiling the water.. ( most likely if your having banging pipes) a simple blockage..

turn the temp on the boiler ( not on the room thermostat) down low ..number 1 and see what happens.. banging pipes and hot water out of pipe into tank means the thermostat is busted.. get a gas safe guy in to confirm.. be safe the thermostat is a control on a potentially lethal piece of equipment.. stat will be pennies wont take an hour to swap out if your lucky might be done for less than 65 quid..

the man from British Gas would be 79 quid i suspect. max 169

So your’e saying it’s spewing boiling water when the immersion heater is heating the cylinder up?

It’s a F&E tank (feed & expansion) that fills the system up as it cools and the water contracts, then as it heats up the water expands and some water will be forced back to the tank, the level will go up and down.

Maybe check the water stat, or take a temp reading of the hot water from a tap, about 60DegC would be about right.

I’m not a plumber but had the same issue and got good advice on here (as always)

The pipe over the header tank is venting excess pressure in the system – the water in the heating circuit is kettling (boiling up through the pipes) causing the banging. In my case it was a faulty thermostat I the boiler which was an easy fix. I guess it could be as simple as turn the temp down on your boiler or shorten the time it’s on for??

having re read your post.. does the cylinder have a combined feed tank on top of it? if so the immersion heater thermostat is bust not the boilers.. test as above repair costs roughly the same.

I think you need to clarify your meaning of:

so its using leccy in morning, gas in evening to heat water.

Do you have the same problem at night? are you using the boiler to heat the water up in the morning and at night or are you using your immersion heater in the morning and then the boiler at night?

Strange it the boiling water is coming out in the morning with just the electric immersion heater on as that only heats the water tanks not the central heating or boiler so I’d have thought the amount of expansion would be too small to push much water to the F&E tank.

Like said if it is the morning only maybe the stat on the immersion heater not working (stuck on), usually immersion heaters have 2 stats one being a protection high limit to prevent this. You must have a big problem if it is boiling the tank, plus a big leccy bill. Make sure you knock the leccy off locally when you fiddle about with the immersion heater, the control stat may be under the immersion heater cover, check both stats.

Check water temp am and pm with a temp sensor.

Worse possibility: ruptured coil inside the HW cylinder and direct HW from the boiler is bleeding into the cylinder.

Expensive.

thanks for the replies chaps, ill try and answer your questions best i can 🙂

So your’e saying it’s spewing boiling water when the immersion heater is heating the cylinder up?

the immersion heater is set from 5am til 7am. this is happening around 7am, not sure if the heater has stopped or is still running at this time, but either way, its near the cut off point.

having re read your post.. does the cylinder have a combined feed tank on top of it? if so the immersion heater thermostat is bust not the boilers.. test as above repair costs roughly the same.

not sure what a combined feed is. altho for those advising to alter the boiler setting, id just like to say the boiler isnt on, its the immersion heater. and yes, ive suspected the stat isnt working on this for a while. sometimes the water when we run a bath is toooo hot, so ive turned the little dial down, but it never seems to make a difference. so i just assumed that bit wasnt working ‘but i can live with that’. so yes, looks like the problem is likely to be the immersion heater.

Do you have the same problem at night? are you using the boiler to heat the water up in the morning and at night or are you using your immersion heater in the morning and then the boiler at night?

we dont have this problem at night. and yes, immersion heater in morning, boiler at night. this is because we werent sure if leccy or gas is the cheapest way to heat water (boiler or immersion?) so we had one of each 😀

You must have a big problem if it is boiling the tank, plus a big leccy bill.

we do have a high leccy bill, always have had 🙁 should have investigated long before now i spose 😳

Worse possibility: ruptured coil inside the HW cylinder and direct HW from the boiler is bleeding into the cylinder.

Expensive.
dont like the sound of that :-/

btw, the CH isnt on, and as for banging pipes, im not convinced they are. wife has said theyre noisy and told me to listen today, but the noise to me seemed to be the hot water chucking itself into the header tank in spurts.

thinking about it….. would it solve (well, not solve but bypass) the problem if we left the immersion heater out of the equation and just used the boiler for all heating duties in the short term?

thanks

Defo sound like the stat, this is may be incorporated into the immersion heater so a fair job to replace but easily doable if you want to save money.

I’d just use the boiler am and pm with immersion as backup. Turn the high limit stat down if you have one to use it as the control stat.

EDIT: Stat may be separate from immersion and just slides in a pocket in the immersion heater, this is dead easy to replace.

We had that problem and it turned out to be a rupture in the HW cylinder as suggested above.

Your cylinder isn’t necessarily heating up from an immersion when on water only. There’s two many variables to decide over the Internet. You need to do 3 things.

Turn it off
Read this http://community.screwfix.com/message/46641
Get a gas man out.

Your cylinder isn’t necessarily heating up from an immersion when on water only. There’s two many variables to decide over the Internet.

we dont have this problem at night. and yes, immersion heater in morning, boiler at night.

Therefore immersion heater? also stops when the immersion timer goes off on timer, I think!

Most likely it’s a shagged immersion that’s boiling the water. But he needs a pro to have a look.

EDIT: Stat may be separate from immersion and just slides in a pocket in the immersion heater, this is dead easy to replace.

theres a little plastic dial fitted into the lagging on the outside of the cylinder, and was set at 60. this is what ive tried turning down before with no success.
is this what youre saying may be the problem and is easy to replace?

also, if as i suspect its been faulty for years, why would it suddenly produce this problem now? or could this faulty part lead to something else failing which has possibly just happened?

ta

EDIT: my mates a corgi/gas safe plumber so will ring him later

theres a little plastic dial fitted into the lagging on the outside of the cylinder, and was set at 60. this is what ive tried turning down before with no success.
is this what youre saying may be the problem and is easy to replace?

That’s a cylinder stat to control a motor valve or fire the boiler depending on the controls. The immersion is usually a 3″ or so plastic cirCular thing with a cable coming out of it in the top of your cylinder.

Take a pic for us.

ISTR bad things can happen with a hot/boiling water overflow into a plastic header tank, and as a result Immersion Heaters in social housing are now fitted with an over-ride safety stat. Dunno if that means a replacement or a mod.

I’d suggest you turn off the IH until things get clarified.

The plastic thingy on the side of the tank will control the boiler.

We hadd the same when i was a kid, tank boiled up,and very hot water filled the expansion tank, thuis then p;poured out of the overflow, onto the garden and killed all the plants, as they literally boiled.

Also there have been cases where the expansion tank overflow has jammed with something, resulting in all that nice hot water overtopping the tank and pouring thjrough the ceiling, or the plastic tank deforming and seriously injuring people in bed below the tank.

http://www.guardian.co.uk/uk/2008/jan/08/uknews4.mainsection

It doesnt make nice reading, get it fixed very soon.

Just an observation How much hot water do you use that you heat the tank twice daily ?

ill get onto loading a pic onto here. we prob have bath or showers in morning, washing machine, dishwasher throughout day, bath or showers again in evening. family of 4.

Modern dish washer and washing machine ? Both use cold water

Not saying your doing owt wrong your the end user but i would keep an eye on it you might be able to save a fair chunk of leccy/ gas/ money depending on the size of yer tank

hmmm….. washing machines a good few years old but dishwashers new. im a bit ignorant as to stuff like this, but i always thought yes, itll either take cold water and heat it up, or use existing hot water. either way itd cost the same? so it just feels right to have it on a couple of hours morning, same at night. im always open to a bit of advice for saving money tho 🙂

Large tin thing on top of cylinder is the heater eleement.

white box with dial is thermostat adjuster

1. Switch power off to heater, even if time switch is off 😉
2. take cover off the heater.
3. The stat will be under the cover.
4. Check the temp setting on stat.
5. Turn down stat. By turning the screw up and down you may hear the stat click at the tank temp if the tank is hot.

6. If problem continues, replace stat. Disconnect the 2 cables, Pull old stat out of cylinder sleeve. Stick new stat in and connect.

7. If problem continues move house

ive switched the power off by the isolating switch, but theres still a display on it. so i thought id check here first 😀

as you can see the switch which feeds into the programmer is off, but theres still a display showing. so is it off? is it safe?? wiring goes mains –> isolating switch –> programming unit –> immersion heater.

looked in the consumer unit and theres no RCD for immersion heater, so i guess its part of one of the ring mains.

cheers

The display will be battery backed so it doesn’t loose the time in a power cut.

So it should be safe.

Always knock the breaker off at the dist board if you’re really not sure and want to be uber safe. I wouldn’t bother though 😆

ive now taken this bit out. is this what i need to replace? with the copper bar too, or does the plastic bit come off and buy that seperately?

cheers

Good job. Replace whole thing, get the right length. The copper bit is the temp sensor probe!

Get one the same, (not a high limit with reset only) shouldn’t cost much.

thanks mate.

what do i google? immersion heather thermostat? any recommendations of internet shops? or would you just go to jacko’s, b and q?

cheers

EDIT:

not a high limit with reset only

what does that mean? 😀

EDIT EDIT:
is this right do you think?

Yep, thats good. That has a high limit built in so it would prevent what you had happen in overheating the tank.

Get the right length. 😉

Set to 60-65DegC.

got one and fitted it thanks, but…. i may have made a slight booboo 🙂

it came with a little white splodge of rubber on the top which i picked off as i didnt think it should have been there. then i realised there were no settings on it, just + and –
so im thinking that was maybe there because it had been set to 60 degrees or something and was there to make sure it didnt move? and ive moved the dial now.

am i right in thinking this? the pic on the link above shows white splodges on the top.

how can i set it right? trial and error, or if 65 is max, turn it to max and then back a bit?

thanks