DIY Doctor

Main navigation

Paranoid About My Header Tank Exploding!

Postby nitro23456 » Thu Jan 10, 2008 8:09 pm

I think most of us have heard in the news about the poor couple whose header tank exploded in the loft and scorched their baby to death in the room below.

I think their hot water cylinder backed up and heated up the cold header tank in the loft til it exploded.

Now in my house my header tank sits above my 3 year olds bedroom (in the loft) and I would like to do some checks to make sure everything is fine.

If I go up there I presume the water in the tank should be cold. Can anyone offer any advice on things that should be checked and things to look out for.

Rank: Foreman
Progress to next rank:
Posts: 346
Joined: Sun Aug 12, 2007 6:19 pm


Simply Build It

Postby bobplum » Thu Jan 10, 2008 9:15 pm

one case similar to the one you are talking about was that the plinth/floor frame was smaller than the the tank so that when the hot water started to enter the tank being plastic it went soft and distorted and the bottom over hanging caused the tank to topple so make sure the floor frame is bigger than the tank
do you have a vent pipe from the hot tank to the cold tank is it hot/warm for just a few inches above the hot tank should be cold after that
the vent pipe entering the cold tank any signs of steam?
had any work done on the hot tank?
can you move the tank in the loft to another location?
or can you move your daughter?
otherwise keep calm it is a very rare thing that happened
Rank: Foreman
Progress to next rank:
Posts: 364
Joined: Tue Sep 25, 2007 7:35 pm

Postby marrtin » Fri Jan 11, 2008 11:33 pm

What makes this terrible tragedy even worse, is it could easily have been
prevented given some basic understanding and a few simple checks. Header tanks are designed to withstand a temporary overflow of boiling water without failing, and it is reasonable to suggest the fault in this particular case could have been occurring for some weeks probably even months before the tank finally collapsed.

In this instance, the immersion heater thermostat failed causing the element to continually heat the water in the cylinder until it reached boiling point. The resulting steam escaped as expected up the expansion pipe into the header tank taking with it quantities of boiling water. Cold water from the header tank would be drawn in to the system via the feed pipe to replace the water expelled from the expansion. Eventually, this continual cycle resulted in the water in the header tank reaching close to that in the cylinder below. Eventually and unfortunately, the tank now full of boiling water finally buckled and failed.


1. Exceptionally hot water from hot taps often discoloured and having an unusual odour.

2. Loud noise from the cylinder similar to a kettle as it approaches boiling
point.(maybe only noticeable after 2am or 3am if the water is heated using a cheaprate electricity tariff.)

3. Loud banging noise from the heating pipes.

4. Water in the header tanks very warm or hot after the heating has been on for several hours.

5. Considerable condensation in the loft during winter months.

The only way to be totally sure is to periodically examine the header tank(s) and ensure the water is always at ambient temperature.
Rank: Foreman
Progress to next rank:
Posts: 374
Joined: Fri Oct 26, 2007 6:42 pm

Postby nitro23456 » Sat Jan 12, 2008 11:07 am

I realise there is more chance of being hit by a bus probably but as martinn says we all may as well check to be sure....... a couple of questions regarding this.

My hot water cylinder in my airing cupboard has four pipes coming from it.

1. The first enters the cylinder at the top next to the immersion.
2. I then have one that leaves the left side of the tank where I would describe the 'shoulder' of the tank and loops down through the floor underneath.
3. I then have two pipes, one at the bottom left and on at the bottom right that has a shut off on it.

The one at the bottom left loops up to the loft and the bottom right with the shut off tap loops back downstairs like the 'shoulder' one on the left .

The only one that is cold to touch is the one that goes into the bottom left that has a pipe up to the loft - am I right in thinking this is the pipe that feeds the cylinder with cold water from the header tank and because it is cold everything seems ok?

Can anyone tell me what the other pipes are for as I presume they are simply taking water out of the cylinder to the upstairs/downstairs taps etc and heating system? hence why they are hot to touch and hotter if I run a tap.

I only have basic plumbing knowledge (as far as taps etc go), but central heating is a mystery to me really, a link to somewhere describing exactly how these things work would be very useful on many levels.

As the heating is on this time of year, my electric immersion is off, and hence the boiler is doing all the work. How does this stop heating the water when it gets to temperature? as the immersion is set to 60 but it isnt being used?
Rank: Foreman
Progress to next rank:
Posts: 346
Joined: Sun Aug 12, 2007 6:19 pm

Postby marrtin » Sat Jan 12, 2008 1:25 pm

[url] [/url]

For a picture of a standard "Y" plan system and

[url] ... eating.htm [/url]

for further reading.

You need to keep an eye on the two 3/4" (22mm) expansion pipes leading up to the loft. Reach up as high as you can, and feel the pipes. If all the pipes are cool or cold, you can be reasonably sure everything is ok. If any are hot, further investigation is required although it is possible depending on the design that in certain circumstances some pipes may be hot to touch and yet the system may be working safely.
Rank: Foreman
Progress to next rank:
Posts: 374
Joined: Fri Oct 26, 2007 6:42 pm

Postby bonzo » Sat Jan 12, 2008 6:37 pm

The pipe coming from the top of the cylinder is the hot distribution. It will split with a vent going up to the cold tank. This vent pipe will be the one dispelling the boiling water if it overheats.

The bottom feed with shut off is the cold feed to the cylinder from the cold tank.

The other 2 pipes on the sides are the flow and return from the boiler through the coil in the cylinder.
Rank: Apprentice
Progress to next rank:
Posts: 13
Joined: Thu Oct 25, 2007 7:51 pm

Postby thedoctor » Sat Jan 12, 2008 6:45 pm

See the projects section. Projects covering hot and cold water systems are in there
Posts: 2525
Joined: Sat Apr 08, 2006 12:15 pm

Postby swindon dog » Sat Jan 26, 2008 8:30 am

I also have a problem my header tank gets very hot it is a small plastic tank ,as soon as the heating/water is put on water flows into the header tank and the water coming out of the pipe going into the tank is hot almost immediately,my system is a baxi back boiler ,also it is causing a lot of dampness in the cupboard from the heat from the tank .
Any ideas
swindon dog
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Sat Jan 26, 2008 8:19 am

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics