Water leak under concrete driveway: how to find / repair without ruining driveway

Forums › Home Workshop DIY › Water leak under concrete driveway: how to find / repair without ruining driveway

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#1832079 27-Jul-2017 10:03

Bung: I think blaming earthquakes is just one of those easy things to say. My neighbour had leak from his pipe in the grass berm just after Chorus had been through burying fibre. Rather than wait I dug down to see what had happened and found the toby had about 500mm of copper before a joint to a type of polybutyline pipe normally used inside. The grey poly pipe had a pinhole split just after the compression ring. The plumber that fixed it by cutting out the split section and adding a short piece said that normally that type of pipe was ok so long as it wasn't exposed to UV. The pipe is much thinner than the blue type normally used.

Your pipe may be copper then joint onto something else close to the toby. Can you see what type of pipe arrives at the house? If it is a joint failure close to the toby you may end up with a cut out big enough to expose it. If and when metering ever arrives you'd need a bigger toby box anyway.

The council guy is the one who suggested earthquakes. Doesn't really matter the cause.

We have no idea where the pipe goes into the house. The council plans show where waste water goes, but not water pipes. Access under the house on the side it comes in is very limited, and I have a shoulder injury that would prevent me going under there to poke around. Once we get the council letter we'll come up with a plan, which will probably start with a second opinion on if there's a leak, then locating the leak, then looking at the options to address. The fix could be fixing the pipe, replacing the pipe, or running a whole new pipe.

The toby box is embedded in a concrete driveway. There's no way you could get a water meter in there easily.

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#1832094 27-Jul-2017 10:29

timmmay:

Thanks for the thoughts. The council guy listened at the toby, the leak could be anywhere along the length of the pipe. The impression he gave is that it's a small leak caused by an earthquake near the front of the driveway, not too far from the toby.

Ahh.. that doesn't sound as bad. I thought you'd heard water actually running under your concrete driveway. That would've pointed to a car-swallowing sinkhole in the long term.

Yes - the most likely spot for a leak to form with ground movement/subsidence/earthquake is a joint or connection being tweaked.

Maybe you'll get lucky and just cutting a plug out will find it.

MikeAqua

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#1832108 27-Jul-2017 11:13

I'd do as much non-destructive investigation pas possible before cutting concrete.

Not just looking for the leak, but where the pipe goes as well as any other services (might be difficult through concrete).

In an ideal world you would pin point the leak cut a small hole, have the leak joined and fit another toby box so the joint can be accessed.

Mike

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#1833566 29-Jul-2017 21:29

I would highly consider just getting a whole new pipe installed. As if you cut open your new driveway, and find that the original pipe was never installed properly / is the wrong type of pipe / it is at the end of it's life. You will have to install a new pipe anyway as a permanent repair.

freitasm

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#1833576 29-Jul-2017 21:44

wellygary:

timmmay:

We had a visit from an engineer from the Wellington City Council. They think there's a water leak under our driveway,

What led to the council's decision,?, is there visible water seeping somewhere

We had a similar problem when the council showed up here. They saw some soapy water down the hill one day and decided to test some houses. They put a blud dye in our water and sure enough it spilled on the street instead of the storm drain.

Insurance didn't pay because they confirmed it was tree roots and was outside the house so they said it was "maintenance".

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timmmay

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#1857203 2-Sep-2017 15:30

The council took six weeks to send us a letter about this. Now we have 14 days to fix the problem or our water may be cut off. There's bureaucracy for you. They have as much time as they need to mess about, but we have severely limited time to get something fixed that could be reasonably complex, particularly if we have to replace the pipe. I bet that council permits to put in a new water connection could take longer than 14 days in itself.

We're going to call in a plumber and have him advise us.

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mattwnz

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#1857216 2-Sep-2017 15:53

Agh Councils grrr!

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#1857300 2-Sep-2017 18:41

You should pressure test for a leak before doing anything else, especially expensive leak detection, cutting up drives etc. Most plumbers will have a hydrostatic pressure test pump which is a pump with a gauge. Connect this to the pipes somewhere on your side of the toby, probably an outside tap. If you shut off the toby, pump it up, you can see if the pipes are losing pressure over a few hours due to a leak. Shut the valves to the toilets, hot water cylinder etc where possble. This will prove if you have a problem first.

I had a similar problem at my house, we had an old galvanised steel pipe under the drive that had corroded and was leaking. I found it as there was a wet patch on our drive continuously. Was lucky as it was cobble stones so could access and find the problem. The galv pipe was only 50mm below the cobbles and had rusted through. We then found it went across our neighbours property and back onto our property and up the side of our long driveway! Half was plastic pipe, the other half galv pipe so a previous owner had a similar problem but did half a fix! I dug a trench down the side of the driveway and found a different route and got a plumber to put in a polyetylene pipe. I also installed a shutoff valve at the house so could access it quickly if there was a problem in the house. Putting the cobbles back properly was a pain and had to do it twice to get them to line up properly, fit and be level.

timmmay

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#1857306 2-Sep-2017 18:55

That sounds sensible. That's why I'm calling a good plumber in Monday morning, rather than going straight at leak testing, I figure anyone in the industry will know so much more than me they'll be invaluable. Plus to do leak testing I need to find the pipe.

Bung

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#1857311 2-Sep-2017 19:01

Kickinbac: I had a similar problem at my house, we had an old galvanised steel pipe under the drive that had corroded and was leaking. I found it as there was a wet patch on our drive continuously.

I find it strange that a leak big enough to trigger a council investigation hasn't caused timmmay any problems so far. I had a fountain in the front garden when my pipe went.

Unless the plumber needs the toby to be shifted AFAIK there wouldn't be any need for permits to repair/replace the pipe.

Kickinbac

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#1857327 2-Sep-2017 19:22

Bung:
Kickinbac: I had a similar problem at my house, we had an old galvanised steel pipe under the drive that had corroded and was leaking. I found it as there was a wet patch on our drive continuously.

I find it strange that a leak big enough to trigger a council investigation hasn't caused timmmay any problems so far. I had a fountain in the front garden when my pipe went.

Unless the plumber needs the toby to be shifted AFAIK there wouldn't be any need for permits to repair/replace the pipe.

Mine was cobble / paving stone so lots of gaps for water to get through. Also depends on what the ground is under the concrete. Mine was clay with a thin layer of scoria.

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timmmay

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#1857336 2-Sep-2017 19:51

It's all concreted, so I might not notice anything. The toby's 40cm down, but then the pipes head down quickly, because the section's on a bit of a slope. I also have subsurface drainage, that black pipe stuff, so it could carry away some of the more obvious signs. There is occasionally a patch that looks slightly damp on the side of what's effectively a small wall.

The council guy told my wife it was an area investigation. They found many houses in our area that had leaks.

If we can fix the leak at the source, that's good. Otherwise we'll have to put in a new toby in a different place, which will involve permits and such.

timmmay

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#1869908 21-Sep-2017 07:46

We've fixed this up now. My plumber said there was no practical way to locate a leak, that leak detectors don't work. We cut up the driveway to replace the toby and put in a new water main. It made a mess of the driveway, the nice dark patterned concrete will have a plain patch that's 2x1m at least. The lawn that the pipe is under now will recover. There was one leak between the toby and the pipe, but being so old there were probably multiple leaks.

As a bonus, the water tastes better through the new plastic pipe than through the old copper pipe. I think that's partly because the water was run for a while - still water in the pipes seems to take on a flavor.

Getting through the commercial grade concrete driveway, digging up the lawn, then putting the lawn back and putting in some concrete to fill the holes. The plumbing parts were probably 4-5 hours and around $600 worth of parts, including fixing a valve or something that was leaking. Total cost was just short of $4000 inc GST.

All in all, annoying, costly, and unsightly, but water is fairly important.

Fred99

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#1869935 21-Sep-2017 08:49

Damn it. My job for this morning is to deal to a sinkhole that's appeared in the middle of our driveway (tar-sealed). Not likely to be water-leak related, but definitely an under-runner washing the clay out from under the base, possibly from a stuffed stormwater system - that possibly from quake damage 6 years ago. Finding the source is (from past experience) practically impossible. Shared driveway - so I'm not bothering with the "committee of residents" who'll be galvanised into paralysis and navel-gazing. The hole needs to be filled now before someone breaks a leg - then worry about if it's going to get washed out again later.

linw

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#1869939 21-Sep-2017 08:51

You got donged with fresh water, me with storm water!

Yesterday a guy in a hi vis jacket and wearing headphones walked our street opening the toby cover and putting a wand down. Sound like a leakage survey?

Wonder how they tell water flow is leakage or just from a tap running in the house?

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