# Gas Supply Pipe Size Query

#### Harry Bloomfield

I dont know if the pipes are colour specific.

Yellow = gas, blue = water, green = telecoms.

#### JohnD

green = cable tv and phone; grey = BT and similar telecomms; red = HV electricity, black = "LV" electricity' mauve = traffic signals

#### fixitflav

Have the regulations changed? I dont understand how I have not had any pressure issues with my current boiler, but now i must go smaller.
A bit of an aside, but looking at the Ferroli 38 manual, it says gas pressure at the boiler must be 20 mbar MINIMUM. The "nominal" supply pressure is 20 mbar, but the regs say it can be 21+/-2 mbar after the meter. So with 1 mbar loss between meter and boiler it can be 18 mbar at the boiler and meet the regs. My guess is Ferroli just quote the nominal figure and haven't bothered to put any thought into it, but they might be trying to give themselves a get-out in the event of a problem. In practice I'm sure the boiler could cope with a lower pressure. I remember seeing data for one boiler which gave an actual minimum acceptable pressure.

#### old duffer

being gas safe registered means they have paid protection money to the same company who collects the TV licence (Capita) so as to say they don't need anyone checking their quality of work. It is not, nor can it ever be, a measure of competence to undertake BASIC maths calculations. You can have the pipework checked by an engineer (a real engineer) who uses maths but what you want to know is can you use the boiler on the gas supply you have.

So, turn everything on FULL...gas fire, cooker and of course the boiler on HOT WATER mode.

Did the boiler stop?
Did the gas cooker go out?
Did the fire go out?
Did any of the devices falter in any way i.e reduced output/water temp etc.
If they did, then your current supply cannot cope with your maximum peak demand..

So you now want to know what it can handle

So boiler on Hot water..
then gas fire....everything still OK?
Then cooker rings...etc etc,

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#### Leon Westwood

being gas safe registered means they have paid protection money to the same company who collects the TV licence (Capita) so as to say they don't need anyone checking their quality of work. It is not, nor can it ever be, a measure of competence to undertake BASIC maths calculations. You can have the pipework checked by an engineer (a real engineer) who uses maths but what you want to know is can you use the boiler on the gas supply you have.

So, turn everything on FULL...gas fire, cooker and of course the boiler on HOT WATER mode.

Did the boiler stop?
Did the gas cooker go out?
Did the fire go out?
Did any of the devices falter in any way i.e reduced output/water temp etc.
If they did, then your current supply cannot cope with your maximum peak demand..

So you now want to know what it can handle

So boiler on Hot water..
then gas fire....everything still OK?
Then cooker rings...etc etc,

Absolutely no problems at all. Looking at my current boiler manual I cannot find a minimum gas pressure, but did see a fault code for low gas pressure. I have never seen the fault code appear on the boiler screen.

We did previously have a gas fire that was often used in conjunctiion with the boiler and i didn't note any issues. The last installer who came suggested that if I used a boiler of a greater rating than the 22mm pipe will allow then it would breach my warranty. I am not one to ignore regs either as i would want it done correctly even those regs are a little pointless or frustrating.

I doubt very much that I would fing a gas safe engineer willing to ignore said to install my boiler in any case. This has turned into a nightmare!

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#### fixitflav

If everything works OK now I don't see why there'd be a problem replacing the boiler with one of similar output. If you want to go bigger it might be worth doing some pressure tests to see if there's anything in hand. Get a length of clear plastic tube to use as a manometer, and measure pressure at the boiler inlet. Also just after the meter, to give some background data. When everything's turned on, and with various combinations if thought necessary.

#### muggles

If everything works OK now I don't see why there'd be a problem replacing the boiler with one of similar output. If you want to go bigger it might be worth doing some pressure tests to see if there's anything in hand. Get a length of clear plastic tube to use as a manometer, and measure pressure at the boiler inlet. Also just after the meter, to give some background data. When everything's turned on, and with various combinations if thought necessary.
The problem is that "it works OK" isn't the same as "it complies with the regulations". Regs aren't there to be cherry-picked

#### fixitflav

The problem is that "it works OK" isn't the same as "it complies with the regulations". Regs aren't there to be cherry-picked
We understand it's working OK now, but OP doesn't know whether it meets the regs or not. If he does some pressure tests he can find out. If it turns out it's say 22 mbar after the meter, and 20 mbar at the boiler inlet (so failing the 1 mbar pressure drop requirement) I doubt if he'd want to switch everything off and get a new, smaller boiler installed, or upsize the gas pipe. But at least he'd know where he stands.

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#### muggles

We know by calculation what the result will be

#### DP

OP, has the gas pressure been checked at the boiler when boiler is at full demand

#### old duffer

The problem is that "it works OK" isn't the same as "it complies with the regulations". Regs aren't there to be cherry-picked
what regulations are these specifically? Can you post a link to them.

#### fixitflav

green = cable tv and phone; grey = BT and similar telecomms; red = HV electricity, black = "LV" electricity' mauve = traffic signals
I thought black was for foul water, but that would usually be 80mm dia and above.

#### Agile

A Gas Registered installer is expected to install a supply pipe which gives 1 mb or less of pressure loss between the meter and the boiler inlet.

Since the pressure loss cannot be accurately calculated as no one seems to know what size/type this 22m of pipe is then it needs to be measured. Easy enough to do.

However, there is another problem! Any new boiler is likely to be fitted to use the existing supply and that will need considerable care to manage the expected pressure problems.

I would also take the view that Gas Safe would be likely to consider the whole boiler installation as non compliant if part of the gas supply was in yellow plastic pipe under part of the building!

I know of an installer who was nearly struck off the register when he fitted a new boiler on an undersized pipe which went under the floor from front to back of the house. The floor was covered in engineered wood and obviously he did not want to disturb that!

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#### pcaouolte

A Gas Safe registered heating engineer who came to quote for a new boiler (not do any work, just to quote) left us with a gas safety warning notice because he had seen a yellow plastic gas pipe emerging from the floor when he was surveying the premises. This was because a previous owner of the property had built over the plastic gas supply pipe. We ended up having the gas meter moved and all of the piping renewed between the gas main in the street and the boiler in order to overcome this problem. I had no concept of how many people Cadent require to move a gas meter a few meters and re-pipe it, 13 people in total!

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