Hoping someone can give me an idea if this is possible.

Having my boiler replaced on Thursday and the gas pipe from the meter to the boiler needs changing from 15mm to 22mm.

This will involve running a whole new pipe, the problem being the gas meter is one side of the house and the boiler the other. I’ve tried tracing the existing pipe but being a newer house it doesnt have floor boards for me to take up easily so its almost impossible for them to run the pipe internally how the existing pipe has been ran.

The other option involves them running a pipe on the outside of the house but I’m concerned this will look silly on the front of the house. Are there any regs saying the pipe can’t be run very low down and under the height of the door threshold?

It would still be above the ground but under the door instead of over the front door in the middle of the house.

Are they putting a combi in hence the need for 22mm?

What about sticking with a system type boiler and a pressurised water tank?

As for the pipe – I don;t think it’s classed as ideal to have it running under a door as it can be damaged. Would be worth making some kind of very robust cover/step that protects it.

Yeah, going to a combi boiler to replace an old conventional boiler and tank.

The pipe would be protected by the threshold of the door which sticks out further than the pipe would so not much chance of damage. The rest of the run is just dirt by it so it won’t be in danger of damage there.

Worked in a few houses where they have had an internal leak,replaced the pipe and the pipe goes round the house at floor level externally, its a real pain when it passes doors without much of a step,threshold as you can sometimes bang it with a foot or tools, materials, best to make a rigid cover for it there.and as its thin copper, its of the floor to stop water getting into the pipes if punctured, or you could bury the yellow hdpe pipe deep but expensive and dangerous if you sell the house and someone digs it up.

I’d be happy to cover it with a conduit of some form to protect it, I was just worried there would be a building reg to say it had to go 4 ft or above in the air and look out of place.

If it can be run low then I’ll ask them to do that and stick a cover over it, cheers!

The other option involves them running a pipe on the outside of the house but I’m concerned this will look silly on the front of the house.

This is pretty much whay they do in most cases as it’s by far the simplest and cheapest option. You see it all the time in Cambridge.

Perfectly acceptable to run it outside. Mine runs up the gable and once it weathered its pretty inconspicuous. I think folks will notice the 2 black cables running to the sky dish half way up the house first off.

And if it is that long, may need to be 28mm or bigger to run a combi.

tricky and becoming a common problem especially in fairly recent new builds.
the reason you need a larger diameter pipe isnt because you have a combi or system boiler its simply that to provide suffcient gas to your new and undoubtedly higher powered boiler than the original
however..
a larger diameter pipe MAY not be essential.. the pressure of the gas is allowed by regs to drop 1mbar in pressure on its journey from the meter to your appliance.. it drops pressure on its journey due in the main to friction and a smaller diameter pipe creates more friction thana larger pipe as does a pipe with sharp corners. eg 90 degree fittings or elbows. this of course makes the calculations fiendishly complex.

SO get the gas chap to fit the boiler to the existing pipe and record the pressure drop. less than 1mbar and bingo no need for further work.. any more and youve some idea of how drastic a re pipe you need..

but yes exterior pipe is common yes it does weather yes it can be painted . it must be positioned so that it could not forcebly be damaged eg alongside a drive way at 2 foot to the ground would probably see some clown drive into it equally under a door is asking for a kick every time you or anyone knocks on the door..

If it states in the M.I’s that the boiler needs 22mm pipe it needs it, always look in the instruction book.
Do you know which way the joist’s run in the floor space? sometimes you can drill into wall (making sure it lines up with the floor space) and see if the pipe can be pushed through to the new boiler position 😀

Not true as it may need a bigger pipe diameter.

They wrote that in instructions as the majority of installers can’t pipe size properly and they manufacturers were fed up going to under gassed appliances.

Most modern boilers are modulating too regardless of being a combi so usually need a larger gas supply.

sorry Bear but what is not true in what i posted? i.e go by the m.i’s

If the length of the run / frictional resistance was too great then you would need to use a bigger diameter. you can’t assume that you can always use 22mm pipe.

We are splitting hairs as you are correct in that MI should be adhered to above all other standards. However there could be situations where a bigger pipe is required.

Op. You say the house is fairly new. What is your base for comparison? Anyhow, in many cases even in relatively old properties, 22mm (3/4) leaves the meter and is reduced to 15mm (1/2) just before the boiler connection. With some minor exploration it could be determined if this is the case. The fitter would then only have to upsize from the point it was originally reduced. Bearing in mind he has done his calculations and it will provide enough gas for the new boiler.
The reason a combi draws more gas than a regular boiler is due to the instant hot water demand.
I can’t imagine TBH that the meter has a 15mm pipe leaving it. Aren’t there any other gas appliances in the house?

What gears suck said. When we had our combo installed the pipe was 22mm through to the kitchen but reduced to 15mm for the old boiler. Fitter just replaced that section for 22mm.

Just to follow up on this, the fitter spotted the 22 mm leaving the meter and you’re right there is a connection somewhere under the front bedroom floor.

For now we’ve fitted an ugly pipe to the outside of the house but will be ripping the floor up to find the other connection and moving the connection to that. The flooring upstairs is chipboard that is nailed down and goes under the walls. I suspect using a circular saw to cut out a section above the boiler will be the place the pipe is joined.

At over 3 quid a meter for 22mm copper, that seems like a awful waste of time and material when removing a small section of the floor is such a simple and easy thing to do.