Doing a new kitchen myself, thought to be on the safe side, got a Corgi
registered company to sort the gas out.

However, I think they may have done unnecessary work.. Thought I'd ask
here to see what others think..

My existing gas point basically needed moving 1 metre, from 1 wall, to the
corner of the same wall. I lifted the chipboard ready for the gas fitters
arrival. On arrival however, he explained that a 13mm gas feed is
insufficient for a double gas oven and 5 hob gas stove, and needed a 22mm
feed, pointing to the underside of the combi-boiler, as an ideal spur. I
kinda went with his recommendation.

A couple of days back, they came back to do the work (I had to remove
additional bits of the old kitchen to facilitate running the new pipe,
hence the delay).

To my suprise, they ran 22mm from the boiler halfway along the wall, then
fitted a reducer down to 13mm, then another meter, did a 13mm spur for my
hob, and the rest of the feed in 13mm.

Crude pic he

http://picasaweb.google.com/lh/viewP...90944950910994


How does this differ from the original setup of extending the original
13mm pipe installation? Surely the flow is restricted by the smalled
pipe? So even the new setup is limited by the last run of 13mm pipe? I
would have understood things, if they T'd off the 22 with 2x13mm spurs,
but they did not...

Have they created unnecessary work???

On 2006-10-08 19:40:35 +0100, "Black Shuck" said:

Doing a new kitchen myself, thought to be on the safe side, got a Corgi
registered company to sort the gas out.

However, I think they may have done unnecessary work.. Thought I'd ask
here to see what others think..

My existing gas point basically needed moving 1 metre, from 1 wall, to t he
corner of the same wall. I lifted the chipboard ready for the gas fitte rs
arrival. On arrival however, he explained that a 13mm gas feed is
insufficient for a double gas oven and 5 hob gas stove, and needed a 22m m
feed, pointing to the underside of the combi-boiler, as an ideal spur. I
kinda went with his recommendation.

A couple of days back, they came back to do the work (I had to remove
additional bits of the old kitchen to facilitate running the new pipe,
hence the delay).

To my suprise, they ran 22mm from the boiler halfway along the wall, the n
fitted a reducer down to 13mm, then another meter, did a 13mm spur for m y
hob, and the rest of the feed in 13mm.

Crude pic he

http://picasaweb.google.com/lh/viewP...llespie&aid=49
83589095688241169&iid=4983590944950910994


How does this differ from the original setup of extending the original
13mm pipe installation? Surely the flow is restricted by the smalled
pipe? So even the new setup is limited by the last run of 13mm pipe? I
would have understood things, if they T'd off the 22 with 2x13mm spurs,
but they did not...

Have they created unnecessary work???

This is a case where length matters.

Resistance to flow depends on pipe lengths and fittings as well as diameter.

Take a look at this

http://www.cda.org.uk/megab2/build/pub124/sec3.htm

The design may well be reasonable.

The acid test would be to make pressure measurements at the meter and
the two appliances and to check that there is not more than the allowed
1mB drop in pressure.

On Sun, 08 Oct 2006 19:40:35 +0100, Black Shuck wrote:

Doing a new kitchen myself, thought to be on the safe side, got a Corgi
registered company to sort the gas out.

However, I think they may have done unnecessary work.. Thought I'd ask
here to see what others think..

My existing gas point basically needed moving 1 metre, from 1 wall, to the
corner of the same wall. I lifted the chipboard ready for the gas fitters
arrival. On arrival however, he explained that a 13mm gas feed is
insufficient for a double gas oven and 5 hob gas stove, and needed a 22mm
feed, pointing to the underside of the combi-boiler, as an ideal spur. I
kinda went with his recommendation.

A couple of days back, they came back to do the work (I had to remove
additional bits of the old kitchen to facilitate running the new pipe,
hence the delay).

To my suprise, they ran 22mm from the boiler halfway along the wall, then
fitted a reducer down to 13mm, then another meter, did a 13mm spur for my
hob, and the rest of the feed in 13mm.

Crude pic he

http://picasaweb.google.com/lh/viewP...90944950910994


How does this differ from the original setup of extending the original
13mm pipe installation? Surely the flow is restricted by the smalled
pipe? So even the new setup is limited by the last run of 13mm pipe? I
would have understood things, if they T'd off the 22 with 2x13mm spurs,
but they did not...

Have they created unnecessary work???

Have a read of the Gas Fitting FAQ - there's a section on this.

By 13mm you mean 15mm?

My guess/feeling/intuition is that they were right and probably the pipes
needed to be bigger still. Quite probably with hob and double oven
the supply in 22mm to the combi is now under sized.

I'm surprise they didn't carry on in 22mm until the first T to the
appliance, there may be some small clearances or other awkwardness.

If you care to list out the following information I or someone else can do
the numbers. It will depend a lot on where the gas meter is located.

Size and Lengths of pipes all the way from the meter to the appliances.
Number of T and L fittings in each pipe.

Rated maximum heat input of each and every appliance.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Surely the flow is restricted by the smalled pipe?

This is where you misunderstand. The smaller pipework doesn't limit the flow
rate, it just provides resistance. A little bit of 15mm won't harm. It is
long runs of 15mm that cause the trouble.

Hence 10m of 22mm pipework followed by 1m of 15mm pipework is almost as good
as 11m of 22mm pipework and is much, much better than 11m of 15mm pipework.
If you see what I mean.

Think of it as a road network, with 22mm being a nice motorway and 15mm
being a twisty B-road, but without any queues. You don't mind a bit of
twisty B-road at the end, provided you cover most of the distance on the
motorway.

I have no idea if their design is sufficient, though. A large cooker and
combi boiler (i.e. at least 24kW, probably more) can be quite limiting on
22mm pipework. My installation has 28mm until the boiler/cooker tee and then
continue in 22mm until the appliances, although the runs for both are quite
long, particularly after the tee.

Christian.