Joining mdpe onto old rough galvanized.

paulieg1988 · 6 Aug 2017

Hi, looking for a bit of advice,
I've got an old 1" galvanized iron pipe supplying my house and I need to relocate my stop cock due to an extension. I've dug down and found the pipe where i need to cut it and redirect. And as luck would have it I've found a Tee fitting with one leg blanked off (used to feed an old out house)

My question is, what are the chances of getting this fitting to undo, without damaging/twisting/ splitting the pipe? And if I did get it off, what fitting could I use to turn 90° and join onto 25mm mdpe?

My other question is, I originally planned on cutting and fitting a 90° philmac transition elbow to join onto 25mm Mdpe. But the galvanized iron pipe is very rough/bobbly, am I right in thinking a transition fitting is never going to seal onto this?
Thanks

Agile · 6 Aug 2017

You don't say which direction.

Assuming you don't need water say in the picture downward direction, then in theory you could cut the pipe say 100 mm away from the tee and then unscrew the cut off bit out of the tee.

Then use an adapter from the female of your tee and a 90 degree elbow and an adapter from MDPE to do what you need.

But like all plumbing jobs there is a risk that something will break and you are going to need good and long Stilsons to have any chance of undoing the tee. I would take 36" Stillsons!

Tony

paulieg1988 · 6 Aug 2017

Thanks for your reply, this makes sense, you're correct in assuming I don't need water in the downward direction. The external stop tap is just the other side of this wall in a brock built inspection chamber (higher ground level other side of wall) would this be an easier connection/higher chance of successful removal? What's the normal connection to these stop taps, compression or a female thread like the tee? Sorry for sounding so

simple

paulieg1988 · 6 Aug 2017

Would this do the job Agile?

Agile · 6 Aug 2017

I virtually never see galvanised water supply pipes.

But would expect they will be used with a stop valve with female BSP connections.

Its unclear to me your layout. But the stop valve being brass will be much more likely to be able to be undone more easily if you have the right tools for the job.

Mains water supplies are meant to be at a minimum of 750 mm below ground.

Tony

paulieg1988 · 6 Aug 2017

Thanks for your time, I'll attempt to remove the pipe from the tee first, then that way i have a "plan B" if that fails and have another bit of the cherry at the stop valve

Agile · 6 Aug 2017

But once you have cut the pipe you will no longer have any water supply if you cannot complete the supply diversion.

Old galvanised pipes can be quite a challenge.

They sometimes shear off instead of unscrewing!

Tony

paulieg1988 · 6 Aug 2017

This is my concern, am planning on getting a plumber in to do it, but still like knowing the various options to hand.
Am I right in assuming a transition coupler won't seal on a rough pipe like this, even if wire brushed as smooth as possible?

Agile · 7 Aug 2017

They can shear off regardless of who is doing it. But a plumber might be able to lessen the risk involved for example by heating the body of the tee.

A suitable sized coupler might well seal, for which I would suggest sanding rather then wire brushing, or after wire brushing.

But on steel might not continue to seal when it rusts after a while. Might also slip off if your mains water pressure is high.

But I would certainly always prefer a screwed fitting as they are more likely to produce a proper joint which will last.

oilboffin · 7 Aug 2017

It looks like 3/4 bsp to me you could cut it off and put a new thread on with a ratchet stock and die and then put a bps fitting onto the pipe and the world could be right.

Ian H · 7 Aug 2017

I think you will struggle to do anything with that T.

We use these to connect onto lead and steel:

They will seal onto a rough(ish) pipe.

Have s look inside the steel when you cut it, it will look like a fat guys artery.

Another option would be to see if the water board will fit you a new stoptap so you can connect directly onto new 25mm mdpe. You might have to say you want a meter fitting but once done you can have them remove the meter and cap its connection.

Agile · 7 Aug 2017

I was called to someone with one similar to that which was leaking on the lead pipe.

He had had it fitted for him a few weeks before as a little cash job for those working on new water mains outside. But obviously could not call them back!

I very carefully dismantled it but could not see anything wrong with it. I was surprised because those guys were fitting them all day long!

So I just put it back together and it was fine.

Never called back to it so I presume it never leaked afterwards.

Motto, maybe a cheap cash job by an unknown person may not end up as the cheapest solution!

Bosswhite · 7 Aug 2017

I would not be tempted to unscrew the Galvanised fitting,

Try a Philmac Pipe fitting, cut the Galvanised pipe, clean off end of pipe, push on the fitting tighten up and continue with new pipe.

This picture shows connection to copper tube, galvanised adaptors are available

Agile · 7 Aug 2017

Screwed steel joints can be very unpredictable.

Sometimes dreadful looking ones come out easily.

Other times nice clean ones can be a real problem.

That is where a Stillson with nice sharp teeth will help to get a proper grip on the pipe.

If the pipe has significantly corroded inside then the steel pipe can even flatten as you try to undo it.

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Joining mdpe onto old rough galvanized.

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