Waste pipe under pond

[PaulDavidSumner]

My other half and I designed our 'dream pond' after careful thought about the location, shape and size. It is in my back garden which is slightly small to medium size. We planned to replace the 'green cancer' in the middle of the garden with a wildlife pond, then have vegetable beds around the garden borders. Unfortunately, I found a waste pipe about 2 feet down while digging the pond. It seems to run lengthways through most of the planned site


Is it feasible to keep the pond on this site, but just have it shallow where the pipe is? Or is it essential to move it away from pipes?

[johnM]

I'm not a plumber or a waste specialist in any way shape or form, however in my humble opinion it not being a permament structure, requiring foundations, it wouldn't be much heavier than the soil etc that you were displacing.

However I wouldn't think it would be a good idea to put any weight directly onto the pipe, are you using a plastic liner of some sort, are you able to spread the weight?

If it is moulded you could build up the ground around it.

For peace of mind you could run it by your local water authority although technically you are responsibloe for the pipes inside your garden so they may be of limited help.

[Muddypause]

What is the nature of the pipe - is it plastic or ceramic? What does it come from and go to? Can you trace it to manhole covers, and work out what it is for? Could it be, for example, rainwater going to a soak-away, or is it foul waste leading to a septic tank or main sewer? Is it actually in use, or is it an old redundant pipe? And what is 'green cancer'?

[PaulDavidSumner]

johnM - the plan is to use butyl liner, so yes the weight will be spread.

Muddypause - the pipe is ceramic. The small area uncovered so far suggests it leads from my house along the middle of the back garden. I will see if there is any way I can find out what it is used for. Green cancer is a reference to urban lawns as they take a lot of maintenance in return for producing very little of value.

[PaulDavidSumner]

Looking at the direction of the pipe, and the fact it looks like it runs under the manhole cover on my patio, my father and I are both of the opinion that this is the foul water pipe running to the main sewer.

[Muddypause]

First of all, I imagine you are aware that clay drainage pipe is pretty fragile, particularly if it is getting on a bit. The ground around it is all that is supporting it and protecting it, so when you disturb it, do so with care. Ideally, the whole pipe run would be set into a bed of concrete, with more concrete capping it, but this is often not the case. I make this comment, not because I think you wouldn't be able to work it out for yourself, but because I, who already knew about this, still managed to put a pickaxe through a clay drainpipe when I was digging recently. Oops.

If the pipe is already capped with concrete, and you can make the pond shallow there, so that the pipe isn't exposed, then I don't see why this couldn't be OK.

If there is no concrete, then you could probably get away with carefully exposing the top three quarters of the pipe and encasing it.

But probably the best thing to do in that case is to replace that whole section of pipe with plastic. It's fairly simple to do - 110mm plastic drain pipe comes in lengths of up to 4 meters, is easily cut to length with a saw, or sections connected together. You link it at either end to the existing clay pipe with a special connector (do this a couple of feet into the bank of the pond, so that it is well supported).

If you plan to make the pond deeper than the pipe, so that the pipe is suspended as it goes through the pond for more than a couple of meters unsupported, build little brick piers or similar under it (I guess you would also need to find a way to seal the pond liner around the pipe). And if it is exposed to sunlight, make sure you use pipe that is rated for above ground use (usually grey) rather than stuff intended for underground use (usually brown). If the pipe is under the pond liner, ideally you would lay the plastic pipe in a bed of pea shingle, though for this sort of thing, it is probably unnecessary.

Obviously it's preferable to do all this when the pipe isn't in use; you can get special bungs to temporarily plug the pipe (at the upstream manhole) if this is not possible - you could probably do it with rags, too, but make sure you can get them out again.


Re: Green Cancer: Just a personal opinion that I know not everyone shares - I happen to think that user-friendly grass is a Very Important Thing in a urban environment. There, children (and grownups) can play without fear of scraping their knees, and they can sit, or lie, or walk barefoot in comfort. And compared to an unpleasant street, it's easier on the eye, too. Surely the real urban cancer is concrete and tarmac, which banishes all life from it.

[Wombat]

I agree with Stew on the green cancer thing - Bill Mollison notwithstanding. We do not fertilise or water ours, harvest it regularly with a push mower so no fossil fuels are used and use the resulting clippings as chook food or mulch or chuck 'em in the composter!

Nev

[Thomzo]

I'm not a great fan of grass. I took up all the grass in my last garden and probably will remove most of it in this one over time. I've already dug great patches of it up. I do use the clippings as chook bedding though or as a mulch. It's quite good at the moment as it's full of leaves so a great mulch.

Zoe

[Millymollymandy]

I thought the cancer in an urban environment was the concrete/paving slabs that people put down where once there was a lawn. Isn't it supposed to create havoc with drainage (i.e. the lack of it) which is one of the reasons there is more flooding these days?

[Thomzo]

That's certainly true around Swindon. There was no reason for the flooding here. I'm convinced it's because such a high proportion of the town is concrete or tarmac.

Zoe

[PaulDavidSumner]

Thanks for the input folks. The idea about replacing sections of pipe so it can run through the pond is new to me and shows again how there are few limits to what you can achieve in a garden. After a few days at work chewing over our disappointment, we have come up with a simple solution. The deep channel where the pipe is will be moved a few feet to the left. The wide part at the bottom can include a shallow area over the pipe - shallow areas are necessary in a pond anyway. The area where the pipe is now will still be part of the designated pond zone - it will all be covered in soil, then I will put the logs, rocks/shelters etc. there and allow it to grow wild. Basically I am getting to keep the original design within the same pond/wild plants and shelters area, just by inverting the shape. I just need to re-fill over the pipe with soil back to ground level, and get it to pack hard again, as it will be pond bank and could capsize when I start to stretch the liner over if I don't give the refilled ground time to settle. One day I will finally be able to post pictures of the finished nature reserve...

[Millymollymandy]

Look forward to seeing it - good luck with the project!