Fitting a gas hob and oven

[Fredxxx]

These are to be fitted in a work surface and a kitchen unit.

I want to do the job right such that if inspected there won't be any issues later.

I've read:

but its a bit quiet in certain areas though gives a good indication of determining leak-rate.

Where possible I was going to use end-feed fittings, though the only demountable fittings I can get are of the compression variety. In the past I have been able to source gas union joints. Is this OK to use compression joints if at the back of the units and under the work surface? Will they be deemed as accessible?

I understand there ought to be a means of isolating the hob and oven. Is it acceptable for this to be a single valve for both appliances. There are "Fan Key Gas Cock"s and "Isolating Gas Ball Valve. Which should I use? I can get the Fan Key Gas Cock in a capillary form, but of course that will require dismantling and reassembly with new grease. I don't have the proper grease at hand, will alternatives be OK?

I'd appreciate any guidance.

[Graham.]

IRTA...

...Oh, never mind.

[John Rumm]

You can use compression joints or solder. Do you particularly need them to be demountable?

Many ovens will use a flexible hose for the final connection with a normal bayonet connector.

Hobs (contrary to popular belief) can also use flexible hoses, or can be rigid piped. The final connection the hob usually being a gas union nut, such that it can be disconnected there.

Yes, I believe so.

A lever ball valve is the most commonly used IME.

(I am not a professional gas fitter - so seek confirmation of the above)

[Fredxxx]

I was aware that flexible pipe can be used, but presumed that a bayonet fitting behind or underneath kitchen unit would be against form! I also thought it was forbidden where a hob is above an oven?

Gas Union Nuts seem to be rather rare beasts and not sold by the likes of Screwfix and not mentioned on some of the more tradition plumbers' merchants websites?

Access will be dire after fitting the kitchen units, such that I'm considering plumbing the hob and oven before fitting the kitchen units to the wall. Then a demountable joint to help fitting of the set of units where an undercounter fridge is going. If failing to obtain a gas union joint I'll use a compression coupler as it will at least be accessible.

Thanks again.

[Andy Cap]

I had a hob fitted just weeks ago by a Gas safe registered installer who said this wasn't allowed and that he'd come across one just that week. So following what you said I emailed Gas safe to ask and have just received the following reply.

"Thank you for your enquiry, generally a gas hob can be fitted using a flexible hose provided that it can be installed in the appropriate manner ie hanging in a relaxed U shape not stressed or touching hot components etc and provided that the appliance manufacturer does not prohibit such method of installations."

I don't think I'll email him though !

Andy C

[John Rumm]

To be fair to the fitters, the BS document in question (BS 6172) did previously have the wrong wording, and it was only corrected in later editions - having said that, it has been in its current form for 10 years!

The 2004 (and 2010) version has: " 11.1.3 A gas hob shall be connected to the termination point by means of rigid pipework or, unless stated otherwise in the manufacturer?s instructions, a flexible connector and self-sealing plug device conforming to BS 669-1"

[John Rumm]

As long as you can get to it to make or break the connection then its quite normal. In the case of an oven they will often have a bayonet fitting in the back of the unit that you can only get to when the oven is pulled out.

Hobs are more traditionally plumbed in 15mm copper anyway in cases where you can get to the underside of it once its fitted. (even if that means the oven needs to go in second).

They are typically just BSP female threaded sockets. Sometimes normal compression fittings. They hob will often come with the fitting anyway.

I think you may be overcomplicating things... bayonet socket on the back wall behind the oven cabinet, then 15mm copper piping round to the right place for the hob inlet with a 15mm leaver ball valve inline.

[Fredxxx]

Thanks, that would be the easiest option.

With the oven removed I could connect underneath as you say, but it would result in a compression elbow, or possibly coupler.

The hob has a male 1/2" BSP.

Sounds a good plan. I note the bayonet socket should be pointing down to stop crud entering, but it would also result in a gentle U behind the oven.

Many thanks for the posts.

[John Rumm]

Is it a taper fitting (probably)? If so a parallel BSP female to 15mm compression would be fine. If its a parallel male then a taper BSP female. Make the joint with gas grade PTFE or suitable jointing compound.

Then you can put the BSP adaptor on the hob, test fit it and pipe up the rigid pipe. Then all you need do on final fitting is make the last compression joint between pipe and adaptor, and test.

The isolation valve can go elsewhere where it will be more accessible. Although there is no requirement for one on the bayonet fitting for the oven, its unlikely to hurt in a domestic environment if it also isolates that.

The down pointing bit is of most importance with free standing cookers, but its the normal approach. A gentle U is ideal since it does not stress the hose or connections.

[Fredxxx]

Is it ok to use a flexible plumbing stick for final fitting to the hob?

It would save a lot of marrying up of pipe and hob. It could also move the only compression joint to a visible location.

Thanks, it is convenient to have both isolated by the same valve.

I think the current one is horizontal!

Many thanks.

[Andrew Gabriel]

I've never seen these used with gas, only stainless steel ones, but not in that circumstance.

TBH, I regard them as a bit of a bodge product to use even with water.

[John Rumm]

I can't really see the need...

You slap something like

on to the male BSP spigot on the hob. Drop it in place, then sort out your pipe run from the wall to the compression fitting on the bottom of the coupler.

Of if you want posh, then there is

(item 12880)

Well it better than pointing up were it could collect crumbs etc.