Gas Pipe

[Mo Thanku]

Hi all, Need some help please,

I am redoing our Kitchen have the few issues with Gas pipe.

The pipe entering the kitchen from the basement is 15mm a big part of it is buried under concrete so I can not have access to it.

Now Because the cooker will be install in new position I will have to reroute the pipe to new cooker point

I was thinking of cutting into the 15mm pipe from where it just enter the kitchen and from that point change to 22mm .

This 22mm(just under 3 metes run) pipe will buried into concrete floor which will tiled over.

The pipe will be wrap in this glue like sticky green tape which my local plumbing shop has given me, saying this is what to use when laying pipe under concrete, I think they called it Dynso tape will this be ok?

From the cooker point the pipe changes into 15mm as it goes upsatirs landing.

In the landing it than changes to 22mm about 2 metrs run till the it than drop down into the cupboard where the boiler is as it drop down it changes into 15mm

*=15mm ==22mm e= elbow *e*****==================e * * * e * * * = = = e ***********=======================

I hope the above drawing gives some idea of what I am talking about. I really do not want to distrub the pipe run upsatirs as it is runing under floor boards and I want to avoid resoldering if I can. I be very grateful for any feedback. Many Thanks MA

[Ed Sirett]

I think you should read the Gas Fitting FAQ below. Quite a bit of your questions are covered therein.

I am fairly sure that your existing gas pipe work is sub-standard and I would be interested to know what the inlet pressure is at the boiler when its going full tilt and you're cooking Xmas dinner.

If you work on the gas installation you become responsible for it. This installation is calling for repipe.

[alan]

Just because it is substandard does not mean you have to repipe it, you are only "obliged" to do that if you are a professional, it would seem the proposal would improve the piping capacity. I had a telephone conversation with CORGI last year and who are aware the advice they give out, if followed slavishly, would create havoc ie "gas pipework undersized so that a gas appliance cannnot run at the manufacturer's design input pressure (and flow)" = AT RISK Well that would knock out around 80-90% of gas appliances. The tech guy gave his opinion that cookers would be ok to 14mb, probably the same for boilers, especially modern modulating, but he would not firmly give this figure for boilers as there are too many variances. The only real danger is cookers and some gas fires on a low peep can be extinguished by the boiler kicking in, but this only happens well below

14mb.

[IMM]

The boiler should have its own dedicated 22mm supply directly back to the meter, assuming a 22mm pipe will be large enough.

Your gas system is well undersized.

[IMM]

NONSENSE!!! Some Ideal pre-mix modulating boilers can operate at 14 mb minimum, so they say. In reality they cut out, bang explode, etc, etc. Modern modulating boilers like the pressure way and the supply constant.

That is why boilers should always be on a dedicated supply back to the meter.

[Ed Sirett]

Yes and No. the 80-90% is probably a fair estimate. However most are only a little out of spec. As 90%+ of installations that don't comply would comply if the maximum permitted pressure drop were 3 mb insteadd of 1mb.

I agree that few appliances would have a real problem at 14mb (except some forced premix burners which are quite sensitive).

AIUI there is an absolute minimum for Transco to supply gas at 15mb with a

1mb drop in the installation pipework that makes 14mb.

The problems of course occur when then you have both very poor service presure and poor installation pipe work.