Gas pipe to boiler

[dp123]

We have a water heater and a gas boiler in the garage at the rear of the house.
The water heater has started to leak at one of the joints so we have decided to install a new combi boiler and get rid of the above.
A local firm came to give us a quote and told us the gas pipe to the existing boiler/water heater is not big enough (15mm) and needs replacing with 22mm.
The meter is in the front of the house and approx 30 meters from the garage (in a straight line) ,we have concrete floors and he needs to run the pipe around the rooms to get to the garage,this has added £600 to the original quote.
Is the info about the bigger diameter pipe correct ,does the additional price look fair?
Are there any boilers that will run off a 15mm gas pipe so we can get away with the upheaval this is going to cause?

Thanks in advance.

 

[Nixt]

This must be the most asked question in the trade and usually because the consumer hates the sound of the answer. So once again, yes you need a bigger pipe and no there isn't a combi that will work on a 15mm pipe of that length as they require more volume of gas than your water heater.

 

[Bahco]

You will probably need 28 mm pipe for some of the distance which is about £15 per 3 metre length.

 

[dp123]

This must be the most asked question in the trade and usually because the consumer hates the sound of the answer. So once again, yes you need a bigger pipe and no there isn't a combi that will work on a 15mm pipe of that length as they require more volume of gas than your water heater.

Due to the amount of people only too willing to rip people off these days (see rogue traders) I'm not surprised the question is asked as often as you say it is.
Look at it from our point of view,we are told we have to install a condensing boiler as they are far more efficient,then we are told we need to run a bigger gas pipe the full length of the house as the boiler needs more gas to run properly.
Can you see where the confusion kicks in?

 

[Gasguru]

And bear in mind the original gas pipe is often way undersized for the old appliance. Blame the goverment - they allow the cowboys to proliferate, regulations are not enforced, and in the highly unlikely scenario of a prosecution the fines are laughable.

 

[dp123]

Thanks for the advice so far.

If i were to get a new combi boiler that will run on the 15mm gas pipe would i be breaking the law having it installed?

 

[Gasguru]

With that lenght of pipework no combi will run on 15mm, most would give problems on 22mm.

28mm is likely to be the minimum sized pipe for a 30m run. Its calculated from tables and experience.

Before you start checking the boiler manuals remember it has NOTHING to do with the gas connection of the boiler By the time you add the friction of bends don't be surprised if 28mm proves too small.

Its illegal to install a boiler on an undersized gas pipe. Many just won't work properly and it can be highly dangerous.

 

[chrishutt]

You might be able to use your existing 15mm gas supply if you go for a small output boiler and a hot water cylinder instead of a combi. However such a small boiler might not be adequate to meet your heating needs, unless your house if quite small and well insulated.

 

[Gasguru]

You might be able to use your existing 15mm gas supply if you go for a small output boiler and a hot water cylinder instead of a combi. However such a small boiler might not be adequate to meet your heating needs, unless your house if quite small and well insulated.

No chance, even a very small boiler (say 1 cubic meter/hour) going by the tables only allows a maximum of 20m equivalent lenght and we no the tables are highly optimistic. More likely a maximum of 10 m with a couple of bends.

 

[chrishutt]

No chance, even a very small boiler (say 1 cubic meter/hour) going by the tables only allows a maximum of 20m equivalent lenght and we no the tables are highly optimistic.

The tables give a flow of 0.88 m³/h for 30 metres of 15mm copper, which would supply almost 10 kW input, more than enough to heat a small, very well insulated house, including stored DHW (although I admit I'm not sure if you can actually get boilers of such low outputs). In any case we don't know if the whole of the existing run is 15mm. It's likely that some if not most of it is 22mm if it's already supplying a "boiler and water heater" (presumably a cylinder).

 

[megawatt]

and he needs to run the pipe around the rooms to get to the garage,this has added £600 to the original quote.

Around the rooms?

Do you mean above the ceiling (under the upstairs floorboards)?

 

[gas4you]

Don't know why £600 is in addition to the quote, as it is a must for the job I would have included this in the main quote.

£600 sounds over the top to me.

Anything more than a 24Kw combi, I would use 28mm for the first 20M and possible 35mm for the first 6M depending on elbows used in the run.

 

[megawatt]

What are you laying G4Y the next North Sea Pipeline ... Ever thought about plumbing gas using 4" waste?

 

[dp123]

With that lenght of pipework no combi will run on 15mm, most would give problems on 22mm.

28mm is likely to be the minimum sized pipe for a 30m run. Its calculated from tables and experience.

.

The original boiler was a combi and ran fine even when the gas fire in the living room was on (now coal fire) and the cooker ,when the hot water side started playing up we blanked it off and installed a water heater next to it.
Both worked fine off the 15mm gas pipe.

When i asked if i could find a combi to run on 15mm pipe i meant a non condensing boiler.

 

[dp123]

and he needs to run the pipe around the rooms to get to the garage,this has added £600 to the original quote.

Around the rooms?

Do you mean above the ceiling (under the upstairs floorboards)?

We have a wood floor in the living room (5 meters from meter to under stairs cupboard wall) and the rest are concrete.
He suggested going under the floor to the under stairs cupboard then taking it up and over the ceiling of the under stairs cupboard ,breaking out running around the top of the kitchen wall to the small room by the back door then straight through this room the bathroom to the garage.
I was not here at the time so do not know why he didn't suggest putting the pipe under the concrete floor other than the mess it would make.