T-ing from a steel gas pipe to copper

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Hi all, before I start I should say to avoid anyone jumping on their high horse this is is *not* something I'm proposing to DIY, apart from the associated works of lifting floorboards etc.

I have Instagroup coming next week to install a new boiler. Because it's a big company, it's been almost impossible to speak to anyone who actually does the work and so I've only had fairly vague proposals of what is going to be done in terms of connecting the boiler to the existing gas supply.

The gas supply to the present boiler is surface mounted and very unsightly - basically it's 22mm all round three sides of a door which is the first thing you see in front of you when you open the front door. So I'm keen to avoid them wanting to do something similar.

I suggested T-ing the supply off the original steel pipe under the first floor, which at the moment only feeds the cooker. This would be better as the steel pipe is hidden inside a dry wall/under the floor.

The surveyor said it wasn't possible to T a copper pipe from a steel pipe, which doesn't sound right to me - to start with the present copper boiler feed is teed off, just much further back. Is this true, or are they just trying to do it the easiest way?
 
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As an RGI, not saying it cannot be achieved, but it would involve (at the very least) cutting out the steel section between the two threaded joints at each end and replacing with, say copper pipe into which a 'tee' can be inserted.

Without X-ray specs, the length of the affected section is impossible to judge, and would of course, mean a whole lot of excavation and making good to achieve.

This assumes that at the very least no other joints are disturbed while carrying this out.

I would respectfully suggest that your hopes are dashed.

DH
 
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I think the main issue here would be that a steel-copper fitting is going to be of a compression type and as you have stated under floorboards, so I guess inaccessible once completed. Which is not allowed on gas pipework.
 
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Hi, thanks for the replies. I did not realise that the whole section between two threaded joints would have to be replaced. I think that would make it a non-starter.

So... second question: is it possible (allowable) to install the new pipe inside the stud wall, next to the original steel pipe? I've stripped off the plasterboard for renovations so the wall is open at the moment.

Here's a photo. Meter cupboard below, copper gas pipe to the right to present boiler which will be removed. Steel pipe in opened up wall to the cooker. New boiler will go in loft, above and to the left.


Under floor:

 
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Cutting into the existing steel under floor is an absolute basic job using basic fittings that are not compression would take a max of 4 fittings for the cheaper option 3 for slightly dearer option depending if you used a slip socket or slip tee.
And take about 15 mins .

But as you have stripped out that wall now then i cannot see any reason why they cant replace all way from meter
 
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I think they will have difficult job running new pipes for gas and heating/boiler pipes in your house as I can see your house is post war prefab BISF type 1A.

Done many work on these, difficult to work cos of not many space to run pipes due to steel joists and shallow joists.

Daniel
 
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The size of gas pipes is an important aspect. It is determined by the distance and gas consumption.

Steel pipe has a thicker wall so copper is more size efficient as it has a larger cross sectional area for the same outside diameter.

But you are the customer, so what you say goes as far as being practically possible, as long as you pay for it.

We don't know in this case but sometimes people getting a free or subsidised installation still expect it to be done as they want it whereas the schemes only cover the cheapest way to do the installation.

It is not that expensive to replace steel pipe by copper and in most cases, depending on access, £300 would cover many cases.

Tony
 
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Well done for spotting it is a BISF house from the photos. I can see how running pipes from one side of the house to the other would be tricky as the steel floor joists run from front to back and there is only room for 8mm microbore CH pipes in the gap between the steel and ceiling boards below.

Fortunately the only obstacle here is the RSJ in the wall just below ceiling level (can just about see it, painted black). It fills the top of the wall, so the original steel pipe avoids it by taking a brief detour into the kitchen (comes out of the wall below ceiling level, then goes into the ceiling void above).

I'm thinking the new pipe should do the same thing, as this can be hidden with some full height kitchen cupboards. From there it would parallel the old pipe in the floor/ceiling void for about a metre then go up inside the wall between the landing/hall to the loft.

As you can probably tell, I don't know much about gas pipes but I have been adding new radiators, modifying the DHW pipe runs etc so I think I have some idea of what might work ;)
 
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I don't read it as Tony saying steel & copper are the same??!! Tony is correct, copper has a thinner wall so if it had the same OD as steel it would have a larger gas carrying capacity. Namely 1/2" steel having roughly the same OD as 22mm copper tube.
 
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Discharge rate for steel pipe is higher than copper
If you mean discharge velocity for the same volumetric flow rate at the same OD, then yes. But I don't really seem to grasp the point you're making?

, volume of steel and copper per 1m length.

1/2" steel 0.00024/15mm copper 0.00014 m3.
3/4" steel 0.00046/22mm copper 0.00032 m3.
When Tony says cross-sectional area, he means the effective cross-sectional area of the bore, not the cross-sectional area of the metal in the pipe.
 
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I think some people need to know the difference between pipe and tube. It might help when thinking about inside and outside diameters ;)
 
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Talking of crushing pipes in a vice I've noticed something concerning. Between the meter and the steel pipe there is about 800mm of lead pipe. Because of the way it's been fitted, it's been bent too much and part flattened. Recently had the meter replaced so maybe it happened then. Thinking this may render any calculations of required pipe size based on boiler wattage, pipe length, number of right angles etc a bit meaningless if not sorted!

Ed
 
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Its a ten minute job to change the lead anyone looking at it would see if its in bad condition and just change it as a matter of course... or should
 
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I don't read it as Tony saying steel & copper are the same??!! Tony is correct, copper has a thinner wall so if it had the same OD as steel it would have a larger gas carrying capacity. Namely 1/2" steel having roughly the same OD as 22mm copper tube.
Hi Richard, if we say 1/2 or 3/4 steel pipe, are they for Outside Diameter or Inside Diameter?
 
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