Tree Roots in Plastic Pipes

[chaoticj]

Hi,

Had a drainage survey last year which found tree roots in the (mainly) plastic pipes at the front of the house. The downpipe on the right takes a little bit of rainwater off the original front bay window roof.

The other 2 downpipes take rainwater off the front single story extension roof approx 15m2 area at 40 degree pitch (built 20 years ago). Original plans show a soakaway at the bottom of the steps. There is a Cherry tree near bay and larger mature trees near the boundary with road - Sycamore, Ash, Horse Chestnut etc.

I can't connect to next doors surface water drains because our drains are lower. I can't connect to my own combined drains at the back as the ground level goes down round the extension and back up again at the side to the same sort of level.

The survey guys gave a quote for a new soakaway with crates wrapped in membrane - £5K. They said soakaway will have failed and doing anything further would be a waste of money.

Had another quote of £1.1K to dig the 3 areas sprayed in red - root balls - this was after putting a camera down. They say some roots will have grown up the pipes from other end. If soakaway is OK when camera'd then make good the ground. But just because a soakaway is shown on the plans - there may not be one at all. New soakaway further £2.8K which would be chippings in the ground with membrane on the top only.

I've done a couple of percolation tests on the grassed area and it drains well.

How would you proceed?

- If the roots were removed, without digging the pipes, would they just grow back again? As there must be gaps in the pipes?
- Would it be cheaper to just dig the pipe nearest the lawn to see where it goes?
- Presumably crate soakaway better than chippings?

Thanks in advance..!

 

[blup]

I believe suction units are available to unblock drains, that may be a option along with jetting or rodding to loosen the material. How did the cctv establish the soakaway had failed, or was it guesswork? The backing up could be due blocked pipes. On that basis I would go for a variant of option 2, more exploratory work. Nothing wrong with an old fashioned soakaway if properly constructed and sized. Even protected trees can be removed if they are a nuisance or may damage property but beware of heave.

This vid is useful overview of the basics and also what can go wrong (read the comments).

 

[blup]

Should add that when I cleaned my own soakaway pipes a lot of the blockage was around the entry point of the drain into the ground where it is trapped.

 

[blup]

Another approach is to identify from the cctv survey where the pipe discharges into the soakaway, dig down exposing the pipe and cut out a section. This will enable you jet wash from both ends.

 

[chaoticj]

Hi @blup the first contractor believes the soakaway has failed, they think root cutting or further investigations would be a waste of money as they think ultimately a new soakaway would be needed so said they are trying to save me money.

We don't know exactly where the pipes go as they can't get the camera past the roots.

I rang someone else, the cost for root cutting is £240 per hour, I'm not sure why it's so expensive? They said sometimes the roots can come out easily, other times it takes 'several hours'.

Apparently where the drain connects to the soakaway, would simply look like a pile of stones, we wouldn't know if the soakaway was running correctly until the next downpour?

I think it might be worth investigating further but not sure what to have done and by whom. Some of the extension gulleys have a connection in the back that was left open. I blocked them off with rubber pressure test bungs, which may now have failed. So I'm not sure if the soakaway could have been constructed in a careless/shoddy manner too..

Cheers!

 

[blup]

It’s expensive because few people have the technology and any work in the ground seems to be inherently expensive/uncertain. So law of supply and demand I guess. My guess is that the blocked pipes are the problem not the soakaway, even if there isn’t one,

 

[Hugh Jaleak]

No point just doing a root cut, without sealing up the pipework at the same time, as all you're doing is buying some time, until the roots grow back again. Assuming solid wall (i.e. not perforated), plastic pipe has been used for the drainage, then the only points roots should be able to ingress is either via the end, or a joint. Given the location of alleged root blockages, those near the building, under the slabs do look a bit of an odd spot to get root ingress, (I'm surprised there's no other evidence of root spread), but without exposing the drainage to see what's going on, it's impossible to say. Have you actually seen the roots on CCTV?

The Bay window drainage clearly predates the extension, is this also causing an issue?

Soakaway's usually fail because they've either silted up, or the surrounding ground has become totally waterlogged and cannot accept any more water. Former may be possible, but if your percolation test is correct, the latter is unlikely. However, this is assuming the existing soakaway was sized correctly in the first place, and that's if they even dug one and didn't just bury the end of the pipe in some gravel.

If you're up to some digging, I'd get your spade out and try and trace the end of the drain, see what, if anything is there before going any further at this stage.

 

[chaoticj]

Hi @Hugh Jaleak it does look like solid pipe - the orange coloured ones. The one near the bay is clay, it might feed into the nearest modern plastic one. The tarmac path has some movement, the main concrete path has a couple of big cracks - I think it's the Cherry tree as the roots can run near the surface - there are a couple showing near the trunk on the lawn.

So you think as the pipes are usually pretty long the roots could have come from the opposite ends? I have pictures on the original drain survey and saw the roots live on CCTV they did say they thought some could have come from the far end of the pipe.

I've attached the drain survey pictures, top left is the bay window..

I think your digging suggestion is a good one, if there is no soakaway then we found our issue. I will dig around the grass near the lowest drain initially.

Thanks a lot!

 

[Hugh Jaleak]

Looking at the photo's, top left is 'Supersleve' clay pipe, which is the more modern version of clayware, that section is knackered, only real option would be to replace the damaged stuff. (If DIYing, treat it like glass, broken edges can be razor sharp.)

Top right, not quite sure there, some root ingress but looks like some soil/silt also there, wondering if that is broken/collapsed nearby.

Bottom, some small roots, but doesn't look enough to impede flow of water or a camera for that matter.

It comes down to what you what to spend really, cheapest option may just be to reroute the downpipes and change the direction of fall of the gutters to send the water to the end of the building and discharge straight onto the lawn. If you want full belt and braces, then there's going to be some digging to be done, although the majority doesn't have to be too deep. Soakaway would be biggest job.

 

[chaoticj]

Hi @Hugh Jaleak I put on my big boy pants the other day and did some digging..

The plastic pipe that takes the majority of the rainwater just goes directly into the ground next to the raised paving. I actually dug a lot of this area out one year as it was full of clay, bricks, stones and other rubbish - so as a flower bed useless as nothing ever grew.

Anyway there was a big root (right hand side) next to the pipe/wrapped around it - might be inside it on the back of the pipe - unsure, the end of the pipe was just full of muck. I assume this is what has caused the paving to slope over the years as the water is not really going anywhere?

The other pipe that goes towards the grass, ends a very short distance onto the grass, it had some pieces of stone on the top and the pipe is sat between some sort of concrete benching. There's large chippings around the pipe but it was basically blocked up at the end. The water does drain away but probably backing up in heavier rainfall, the bottle gulley had an open connection in the back which I'd blocked with a rubber test bung but apparently that's fallen out, so explains why the wall is showing wet after rain.

Anyway I've no idea how much depth the chippings have but they don't look like they would be doing much. It's really close to the extension.

I'm not sure if it's worth doing any more digging or just look to a modern crate style linear soakaway 5-6m away from the extension, wrapped in membrane (not the bottom section)? with catchpit for peace of mind. Doing the digging for circa 3 hours really took it out of me and I got ill for over a week at Easter!

 

[Hugh Jaleak]

Methinks someone couldn't be bothered to do the job right when those drains were laid. I think its time probably to bite the bullet, and sort it out properly, but at least now you know what you're faced with.

There is going to be a fair bit of digging required, it seriously isn't worth making yourself ill over it, and I think you're pretty confident of what you need doing, so I'd be drawing up a spec and asking interested parties to quote for digging and building a crate soakaway, and connecting up existing drainage to it as required.

Note as rainwater going to a soakaway, the downpipes can be directly connected to the drain, although given the proximity of the trees, I would strongly suggest gullies are fitted at the base of the downpipes to catch any leaf debris, or other detritus and prevent it reaching the soakaway.

 

[chaoticj]

Hi @Hugh Jaleak I'm getting a revised quote for what is hopefully over specced.

My main concern is that after about 300mm the ground is pretty much solid clay.

I read about digging a hole 1.2m deep to check the water table. Well I got to about 1m deep and from 0.3m to the full 1m it's solid clay. Also there was no rain for weeks. We're in Lancashire.

The contractor mentioned about digging below the clay for the soakaway.

But I don't know how deep the clay is? I've read online it could be several metres? Will the soakaway still work?

Thanks!

 

[Hugh Jaleak]

Soakaway is unlikely to work in clay soil, you could do a percolation test, but I suspect it'll prove what you already suspect. Unless the Contractor has done boreholes to check for the depth of the clay, they too could be on a hiding to nothing. How far to dig down? How long is a piece of string.

If a soakaway isn't feasible, and available surface water drains are too high, is there any scope to connect to the Foul Drains?

 

[chaoticj]

Hi @Hugh Jaleak I did a percolation test a few weeks ago following a YouTube video and the 300 x 300mm test pit 24 hours after being filled up drained really well. Just don't want to spend megabucks on the soakaway and still have a problem x years down the line due to the solid clay.

With the foul drain it's the same issue as the surface water drain, foul is at the back of the extension, the same level as the front, so how do you bring the front drains around the side of the extension which is lower and then back up to the same level?

Assume it would need a water storage tank and pump? I have emailed local Building Control re: the clay to see if they can advise at all from a local perspective.. thank you.

 

[cdbe]

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