25mm MDPE leaks water but not air, how?

[Ian H]

I did a job last week that should have been simple but wasn’t.

The 25mm MDPE was showing on the meter to be leaking a litre in 45 seconds.

I dug onto the pipe at the point of entry into the property 40mtrs away and capped the pipe, it still leaked.

I connected my kit which can block the pipe and fill it with air at any point and at no point did the pipe loose air pressure. Even if I didn’t block the pipe, using the meter to block it, it didn’t loose air.

I don’t understand. Could the air somehow seal a fitting that leaks water?

 

[dilalio]

So you have a length of mdpe with your test kit at one end and capped at the other and there's no loss of air pressure right?

But when you remove your kit and reconnect pipe to the meter (still capped at end of run) it leaks water?

Is that the test setup or are there other fittings en route?

Could it be that the air pressure is sufficiently higher than the water pressure to close up a leak/pinhole?

Does sound baffling... Could meter be faulty and leaking?

 

[Ian H]

So you have a length of mdpe with your test kit at one end and capped at the other and there's no loss of air pressure right?

But when you remove your kit and reconnect pipe to the meter (still capped at end of run) it leaks water?

Yes to both of those

Is that the test setup or are there other fittings en route?

Could it be that the air pressure is sufficiently higher than the water pressure to close up a leak/pinhole?

There could be a joint on it but no Tee offs.

Possibly but usually it would open up the hole

Does sound baffling... Could meter be faulty and leaking?

I thought that so dug at the meter and capped off and it stopped. I dug at 20mtrs and it stopped. Then I overlanded the last 20mtrs and it stopped.

So i’ve narrowed it down to 20mtrs but can’t pin point it. Very strange.

 

[dilalio]

Possibly but usually it would open up the hole

I was thinking that something has pierced pipe from outside and the extra air pressure pushes that protrusion, that's coming into the pipe, back out, thus sealing it... it is only a thought

 

[Ian H]

You might be right

I’m back tomorow to do some more digging at 10mtrs, 5mtrs, 2.5mtrs...

 

[dilalio]

You might be right

I’m back tomorow to do some more digging at 10mtrs, 5mtrs, 2.5mtrs...

Can you not mole a new length through?

 

[Ian H]

I could but we hire the mole kit in but can’t get one tomorow. We should be able to do 4 digs in the day.

 

[dilalio]

I hate digging

 

[Ian H]

I hate digging

Wierdo

 

[dilalio]

Wierdo

If I have to start digging on a job, then I have fu¢ked up Royally

Edit... "again"

 

[Ian H]

I found the leak by fluke.

1st dig done and I could see it flowing in from 1 end so extended and found the MDPE to be split where it was sat on a stone, just like black alkathene does.

These buildings were built 10 years ago.

Still no clue why it didn’t leak air at 2bar.

 

[dilalio]

Still no clue why it didn’t leak air at 2bar.

That's the difference between hydraulics and drybollox

 

[Ian H]

I’m on may way home now via the beer shop.

Happy new year to you all

 

[dilalio]

I’m on may way home now via the beer shop.

Happy new year to you all

View attachment 155597

Yeah. You too dude.
Top marks for going to work today...
I coulda, woulda, shoulda but didn't

 

[Nige F]

I found the leak by fluke.

1st dig done and I could see it flowing in from 1 end so extended and found the MDPE to be split where it was sat on a stone, just like black alkathene does.

These buildings were built 10 years ago.

Still no clue why it didn’t leak air at 2bar.

Maybe because air (@ 2 bar)can be compressed and water cannot, so water will force through a closed split. No such thing as fluke, M8