Rerouting gas to a different part of the house

9 Sep 2013
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United Kingdom
Hi all, I'm just about to buy a new house and have a lot of changes planned. The first step is replacement of a back boiler/tank heating system with a combi-boiler. Ideally I'd like to install the new combi at the rear of the house but the gas supply is at the front - I was wondering whether it is possible to run the gas pipe inside the house (under the floorboards) as shown in my second diagram.

Here is the existing layout (as best I can tell):

There is a gas meter on the front wall of the house, the gas pipe runs inside the wall until it enters the chimney breast (which is on the party wall - the house is a semi) where it feeds a back boiler and gas fire. Then the gas pipe runs up the side of the chimney to the ceiling, over a supporting wall into the kitchen where it feeds a cooker.

I would like the pipe rerouted as follows:

Up the wall (either outside or inside) of the house until it reaches ceiling height, then through the ceiling void until it reaches the point where the joists are already notched out for heating pipes. It splits into two, with one leg heading off to feed the cooker. The other leg crosses the joists using the notches before turning again and heading off through the ceiling void to reach the new boiler at the rear of the house.

Some questions anticipated:

Q. Why not put the new boiler in the kitchen?

A. Almost all the external kitchen wall is taken up with windows, with upstairs widows above them. I don't think the flue would be far enough away from the neighbours property or the various window openings. If I put the boiler where it is shown on the plan then it will be in the utility room/downstairs toilet (once all the other house modifications are finished) with no windows near it.

Q. Why no gas feed to the fire in the first room?

A. Because I'm going to remove the fire and chimney breast.

Also I'm aware that I can't do this myself, I have to get a gas safe registered professional to do the gas work. Ideally I'd get them to visit to cap off the gas at the meter, then I'll remove the old heating system and fit the new water pipes etc. and then call them in a second time to run the new gas pipes and fit/commission the boiler. Does that sound reasonable?
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All sounds generally reasonable.

Have you considered the loft for the boiler?

Thanks for your reply, Tony, that's a relief! I was worried there would be some sort of regulation on how far you could run gas pipes inside a house.

I hadn't thought about putting the boiler in the loft but on reflection I think it might cause problems for later jobs in the house.

One of my plans is to strengthen the loft floor so I can use the loft space for storing reasonably heavy stuff without worrying about cracks in the first floor ceiling. To do that I think I'm going to need to fit steels (also needed to support what is left of the chimney up there) and larger joists and I'd prefer not to have to work around gas/water pipes when doing that work.
Bear in mind, the length and number of bends used will determine the size of pipe needed, which will in turn affect the size of boiler you get.
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Hmm, I hadn't considered that either. In the new layout the run from the gas meter to the tee is 18ft. From the tee to the cooker is 12ft. From the tee to the boiler is 28ft.

I was thinking of getting an intergas boiler and asking the plumber to advise on the size based on the eventual layout, which is going to be: One upstairs shower room (no bath) with basin, a downstairs toilet with basin and a kitchen with basin. In terms of size the house is a small three bed semi with seven radiators.

I was hoping to get away with fitting the 24/18 model, would I have to go bigger because of the gas pipe?
Your gas fitter on site will advise, if anything the gas pipe could restrict the size of boiler.
Ah, now I understand. Long runs and bends restrict the flow so it becomes harder to feed appliances that consume a lot of gas. Hopefully my boiler will be quite small but, as you say, I'll get the fitter to advise on what he thinks best. Thanks for your advice, gigz.
As a VERY rough guide a 24 kW boiler can be fed with about 20m of 22 mm tube.

But it needs to be calculated EVERY time by the Gas Reg engineer who is going to fit it.

Longer and part of the tube will need to be in 28mm. Most effective to do the bit near meter with many elbows in 28 mm.

It sounds like I'll be okay, I was a bit worried for a moment that the distance would mean that I'd barely get enough gas trickling out at the far end to boil a kettle!

When it comes to running the pipe from the gas meter up to the ceiling can it be buried in the wall?

The existing pipe is sort of half-buried with a bit sticking out of the plaster inside the house but that was done in the 90's, the regs may have changed since. I don't want to box it in so if it can't be buried and plastered over it may have to be run on the outside wall.
There are all sorts of rules about where gas pipes can be put and your installer will advise you.

Mr vogon. If it please you sir, and Tony will happily listen to your poetry on my behalf ;)...... but what software did you use for those rather nifty images?

Nice to see a sensible attitude to advise given on here for a change too; )
I was also impressed by those sketches.

Was even going to make a comment but decided to keep my reply short and concise.

I expect poets know the difference between "advise" and "advice".

The program I used to produce the drawings is called Sketchup Make, it is a free download (for non-commercial use) from here:

It's just about the easiest 3D design tool to use, you draw flat shapes and then push and pull them around to make them 3D. For instance you can draw a rectangle, use the offset tool to make a smaller rectangle inside, then pull up the outer rectangle to make walls. If you draw a small rectangle on the side of the wall you can push it in until it disappears - those are your door and window openings. If the door is too short you just push up the top until it is the right height and so on.

After a bit of practice it's possible to knock up fairly complex drawings quickly. I made a model of the house as is (after taking measurements), and I've been using it to see what happens if I blow out this or that wall, or move a doorway etc. and how I can position furniture. Much less sweating and cursing doing it this way :)

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