Locating drains access chambers in garden

[Maurice]

Recently had a blockage in the external drain into which the kitchen sink discharges.

The guy cleared it with difficulty, because he could not find the drains access chambers that we knew must be out there somewhere. (We haven't been here very long.) Discovered later that the previous owners (who were very keen gardeners and flower club members) had covered over the lids with a layer of gravel and then a covering of small pieces of grey slate all over the kitchen garden flower bed. (All looks most neat...)

Having managed to extract from the previous owners the approx whereabouts of the two chambers, the $64 is: How to locate them (without digging vast areas up)?

Presumably the answer is "A metal detector", but then the next question is: What sort of metal detector could reliably pick out the metal drain access chamber cover without screaming every time a small piece of metal is detected?

[News]

In message , Maurice writes

My first thought would be a pointed iron rod. Just shuffle the slate and poke the ground. A fishing rod rest may suffice, but ideally one of those rods used by highway maintenance teams etc.

[S Viemeister]

I've used an old fishing rod to locate the cover of a septic tank, hidden under deep layers of moss and weeds.

[Roger Mills]

Just wait until it snows. The warmth from the drains will ensure that the area above the covers melts first.

They really need to be accessible. Once you have located them, you could build up the chambers by a brick course or two, and then fit lids of the sort used on block paving drives. You could fill the lids with something decorative to match the surroundings.

[Maurice]

Tried that, but he gravel layer is compacted to the point where the rod can't penetrate.

[Maurice]

Ah, yes! Reminds me of a story about Duke University in N.Carolina I heard whilst out there.

Eisenhower was one of the governors, and during the building phase someone asked where the footpaths should be placed.

"Wait until the college is inhabited, and see where they walk" was his advice.

[Tim Watts]

Metal detector assuming they have metal lids and/or frames.

If they are all plastic - bit trickier. But what about a sharp metal rod and just probe the ground - they are unlikely to be very deep.

[Martin Brown]

A midsized neodymium super magnet on a piece of string.

Or a pretty basic metal detector with the gain turned right down.

It will scream like crazy over an area of at least 2' square (unless the lid is that modern dense black plastic).

[spuorgelgoog]

The official answer is stick a drain rod down with a CAT transmitter on the end and then walk over the area with the CAT scanner.

Or try dowsing rods.

Owain

[Capitol]

I used a 1M drill bit in a battery drill.

[Capitol]

Having recently found the drain covers, I was intrigued to find that it is very difficult to find a plant holder off the shelf, which is drain sized, to put on top of them. I finally decided on a 500mm square one which is too tall but haven't yet purchased, pending further searches. Most plastic rectangular/square plant pots, max out at 400mm leaving very little choice.

[Jeff Layman]

I'm surprised that the guy didn't have CCTV available to check what was causing the blockage. He could then have used the CCTV to locate the access points with reasonable accuracy from the inside of the drain.

[Maurice]

The lids of the ones elsewhere in the property are the old-fashoined metal ones.

[Maurice]

He's not particularly hi-tech, but he did have small metal detector which did find some metal bits... (But at the time I didn't have the approx positions.)

[Maurice]

Actually that might do the trick here. (No battery drill, but got long cable.)

[Bob Eager]

I work in a university, and one of the previous Heads of Estates said he did exactly that. The process repeats every few years as new buildings appear and the routes change a little.

[Tricky Dicky]

If your neighbours access chamber lids are visible then yours will probably in line with them and probably located at about the same point in relation to the building.

Richard

[Martin Brown]

Only in a row of near identical houses built at the same time. But it is certainly worth a try if you can see neighbours drain covers in line.

My main drains access point is in my neighbours garden and so on down the road. We have some drains access points for our house on our land where the septic tank was but the most important one for each house is in a neighbours garden. It is a quirk of how the village grew in the Victorian era followed much later by mains water and then sewerage.

The water comes from Northumberland but the sewage goes to Yorkshire.

[Chris J Dixon]

Apparently the term for those beaten tracks that appear where none are provided is "Desire Paths".

Chris

[Chris J Dixon]

My drain cover is 500 x 600. After experimenting this year with a couple of cheap plastic window boxes side by side, one of my winter projects will be to build a wooden planter to fit exactly.

Chris