Soakaway recommendations, please... - I have too many choices to make!

[Midahed]

Hi,

Sorry for the long post...

I have a rainwater downpipe on the corner at the front of my house that serves an area of roof of approx 35 sqm. It feeds into an open gully that is set into a concrete path that leads from the front door to the boundary of the property.

The gully has been blocked for a while and, on investigation, I found that it has tree roots growing out of it.

I cleared it enough to find the likely direction of the outflow pipe and dug down in an area of the driveway where the pipe should emerge from beneath the concrete path.

I think I've found the original soakaway. The pipe ends in a rubble-filled (and totally silted) area that's partially beneath the path and partially beneath the gravel driveway that runs parallel to the path. It's 3m from the house.

I can see that tree roots are entering the pipe where it terminates in the old soakaway, but without digging up the rest of the path (and an access ramp into the front door), I can't comment on the condition of the rest of the old glazed clay pipework. Given that it's protected by the concrete of the path, it should be OK, but who knows?

I did break up a bit of the concrete around the gully to inspect the pipe at that end. There's no evidence of damage or tree root invasion, so it's possible that the remainder of the pipe is undamaged... but equally it might be broken elsewhere... It's almost certainly been there since the house was built in 1936.

My first thought was to get a drain clearance outfit in to clear the roots and internally inspect the pipe, but then I got an idea of the cost! Given that it would be wasted expenditure if it turned out that there is further damage to the pipe, it seems better to just go ahead, rip up the path and ramp and lay a new drain.

However, if I do that I then have a decision to make regarding the location of the soakaway....

I could dig out the original, but that would mean it would be partially in the driveway and, presumably, prone to subsiding - especially when the occasional skip delivery lorry drives onto it! I also thought that digging out the original location would be hard work because it's mostly broken bricks, whereas digging a new location would be comparatively easy because, once down 300mm it's like digging on a sandy beach.

So, I could put it in the front garden where I wouldn't have to be concerned about structural stability. However there are a couple of trees in the area which means I'll inevitably have to cut through a few roots. The other issue is that there isn't enough space to be able to comply with the 5m from building and 2.5m from boundary rule. The best I could achieve would be 4m from the building and 1m from the boundary fence (on the other side of which is a public asphalt-covered pavement, a grass verge and then a road).

My understanding of the regs is that I can dig out and renew the existing location (despite the fact that it's only 3m from the house) without involving Building Control, but a 'new' soakaway would technically require their involvement.

Is that right? If so, how do they normally deal with areas where it just isn't possible to be both 5m from any building and 2.5m from the boundary? Would you expect them to allow a compromise as I've suggested?

The subsoil here is pure sand. When installing a soakaway in my back garden years ago as part of building an extension I went down nearly 2m and there was never any sign of water. Same for the extension footings.

From the 'how big' section on soakaways on this site, there doesn't appear to be anything in the formulae that takes account of the range of difference in soil absorption rates that could be encountered. I'd expected to find that I could get away with a slightly smaller soakaway given that I'm on such dry sandy soil. Assuming I locate the pit in the front garden, rather than in the driveway, I'd planned to use the 'milk crate' system to get the maximum useful volume for the minimum sized hole. But the formula says that for my 35 sqm area of roof I still need a soakaway that's about 0.6 cubic metres in usable volume. No allowance is made for that fact that it's in sand as opposed to less absorbent soils.

Is that right, or have I missed something?

So, given the choices, what would you do?

Use the original location that's partly in the driveway - and, presumably therefore have to dig a bigger hole then fill it with chippings or rubble to give it sufficient structural integrity for a driveway location?

Relocate it into the garden area, put up with having to chop through quite a few tree roots and use the milk crate construction to reduce the size of the hole to be dug?

Involve Building Control or just get on and do it?

Finally, what's the best root-proof geotextile membrane? I've looked at the Terram site, but I'm not sure which is the best product to use. If I'm going to do this I want to make a decent job of it and ensure that roots don't cause the same problem again in a few years time.

Thanks,

Mike

[flowjoe]

The existing pipework can be root cut and relined to prevent any future ingress, no need to rip the path up if the pipe work hasn`t collapsed.

Widen/extend your soakaway and install the storm water crates shown in the main site, wrap in a geo textile.

Don`t bother with buidling control as its a repair and not a new installation.

There are calculators on the web to work out your roof volume.

[Midahed]

Thanks flowjoe.

When you say the existing drain can be root cut and relined, that doesn't sound like a DIY job. How is it done?

I'd like to use the 'milk-crates' because they provide more effective soakaway volume compared with the old rubble/chippings approach. However, I assumed the creates aren't structural, so shouldn't be used in a driveway unless the hole is capped using something that is structural like steel or reinforced concrete. To be honest I don't want to have to build something like that, so I assumed that I'd have to use chippings to fill a driveway-sited soakaway (and would therefore need a much bigger hole in the first place in order to achieve the required 'effective volume' of 0.6 cubic metres for my 35 sq. metre roof area.

I could do that OK and, yeah, I don't want to dig up the path and ramp unless it's absolutely necessary, but I also don't want to have to pay out for expensive specialist contractors to do the job of 'fixing' the existing drain. Looking at the cost of getting a Dyno-Rod look-a-like to clear the roots led me to believe that it would be cheaper for me to demolish and re-build the path. A bit more work, but at least it's a DIY job.

However, it would be useful to have a bit more info about the root cutting and pipe lining option. Who does it? What's involved? Is it expensive?

[Mikey_C]

the osma/wavin aquacells (milk crates) have two types, one is structural (with 0.5m of soil coverage) (blue) and one is not (green). flowjoe is right pipes can be de-rooted and lined, but I don't think it is a diy job, relaying with plastic and path reinstatement probably is. Also as Flowjoe says soakaway replacement doesn't require building control involvement, I take it the failure hasn't caused any structural problems with the house? however, the further you can move it from the current site, away from the property the better, whilst still doing a replacement :;):

[flowjoe]

Pipe lining is a specialist job but there are plenty of us doing it, its not a DIY thing because of the equipment required, cameras, jetters etc.......

Speak to your insurers you may find you are covered for root ingress to your drainage system, but don`t mention it runs to a soak-away or they may have you on a technicality.

The crates are easy enough to install Tony has a page on the main site covering this.

[Midahed]

Thanks for the info about the structural crates, Mikey_C. I'll look into that a bit more. If they're intended for use in areas like driveways and can withstand the weight of a skip delivery lorry now and again, I would at least have a choice as to where to site it.

I googled for information about root cutting and lining of drains. It looks expensive - the ones I saw use an epoxy insert which is pressurised to expand it out to the full internal diameter of the original pipe before being cured in situ. I've laid a few drains in the past and am not averse to using a big Kango to break up a few feet of path, so I think I'll end-up doing that. Besides, the path is fairly old and tatty and 'er indoors has been angling for me to replace it for ages so I can get both jobs done at once and earn some brownie points at the same time.

Our Building Control guys are a helpful bunch - I've had to get their advice a few times in the past - but I see no reason to, er, trouble them with something so trivial as the clearing and rebuilding of an existing soakaway :;):

No, there's no structural damage. Part of the reason for exposing the area around the gully was to see if there was any evidence of erosion. There isn't any as far as I can see, but I'll get a better picture when I get the path up and remove the entire pipe and gully and can dig down a bit further towards the footings.

As a matter of interest, is there a recognised way to 'test' if an area has been subject to erosion? Dig small trial holes and visually check the state of the subsoil? Bang in a steel rod and feel for soft spots?

The ground is so well drained (we're on the top of a sandy hill) that I can't imagine it will be a problem, but if I'm going to expose a bit of the ground in that area, I might as well know how to check it properly.

[Midahed]

...Speak to your insurers you may find you are covered for root ingress to your drainage system, but don`t mention it runs to a soak-away or they may have you on a technicality.

Thanks flowjoe. Good point!

What was supposed to be a simple job of clearing what I thought was a blocked gully has turned into a fairly major job. Still, I'm retired with plenty of time on my hands, so it will keep me entertained for a while. And the weather at the moment is great for this type of job

As it turns out I've decided to remove the path, and tidy-up the whole driveway and front garden - I need to scrape off a load of soil, lay down some anti-weed membrane and get some new pebbles. Sorting out the soakaway is becoming incidental...

[Midahed]

I've just started pricing up a soakaway based on the Osma/Wavin Aquacell range of products.

Blimey, they're expensive!

OK, it's Plumb Center prices, but the best part of £100 for a single Aquacell blue crate (I need a minimum of four), £50-£80 for ordinary adapters and fittings that I expected to cost significantly less than £20, and a whopping £500 for a silt trap!

Surely, they're having a laugh?

Are there cheaper equivalents from other manufacturers, or are there Osma/Wavin suppliers who are significantly cheaper than Plumb Center?

Suddenly the old-tech solution of a rubble-filled hole is looking more attractive by the day

[Dave_L]

Wavin blue crates - a couple of weeks ago I was counting them so I could sleep!





306 of the buggers fitted up on a project we were involved in. I know the retail price is about £81+VAT each, but surely shopping around should bring that down considerably......

Got a local city drainage outlet?

[Midahed]

Ha ha - I don't need quite as many as that. I bet your company paid a darn sight less than £81 each for them!

I looked using Google and Yell.co.uk and there doesn't seem to be anyone called city drainage in this area (Bedfordshire).

I thought Screwfix might do 'em, but it doesn't look like they have aquacell or anything similar on offer.

Our local builder's merchant is Jewsons. On the basis of past experience, they're not normally very competitive on price, but I'll give them a call.

If anyone knows a good supplier for this stuff who doesn't require a bulk order, I'd be interested to have the details.

I see that both Marley and Polypipe have a similar product, but again they're priced much the same as the aquacell range

[flowjoe]

Google
Discount Plastics, Stanley Green, Cheadle, Manchester.

They have just started to stock crates from Fernco so may have some deals on.

The logistics could add to the cost but they may work with a distributor down your end

[Midahed]

Thanks flowjoe. Much appreciated. As it happens my son lives in Manchester, so logistics may not be that much of a problem. I'll give them a call tomorrow.

I also found www.sewageservices.org who do the blue aquacell crates at £45.83 inc vat. Still not local, but at least the price is getting more sensible.

Thanks for all your help.

[Mikey_C]

keyline builders merchant did them for about £25+vat, when I last used them. Build your silt trap out of concrete blocks or don't bother, you are only running roof water into it you shouldn't have to many foreign objects, put decent gully at the bottom of your down pipe and clean it out regularly. You should be able to get fittings and pipe cheap enough from somewhere like screwfix or toolstation.

[Midahed]

Thanks Mikey_C. It looks like the blue ones from Keyline are just short of £52 (inc vat), and the standard green ones are just under £36.

The big bonus is that there's a Keyline place that does civils stuff just down the road from me in Milton Keynes.

Thanks for all the help from everyone. This is a great site.

All I have to do now is dig the hole....

Maybe I'll eventually upload a picture of my 4-unit soakaway to compete with Dave_L's little project

[Midahed]

[Edit] Please ignore the question below. I now know the answer

I sent an email to Wavin technical support a while ago asking the same thing, but hadn't had a response. I've heard from them, today, saying that each crate comes with three clips and two shear connectors.

I've still got to dig the hole and it's too darn hot at the moment. Maybe if I leave it long enough it will dig itself?





Can anyone tell me how many clips should be used to lock aquacell crates together? I've read all the documentation on the Wavin website, but (unless I've missed it) there's nothing saying how many clips are to be used.

Same thing goes for the shear connectors.

I'll be using four crates to construct a cube 1m x 1m x 0.8m.

I've also noticed that the 6LB102 part number for the shear connector lists it as a 'spare'. The use of the word 'spare' implies that one or more shear connectors is normally supplied with each crate. Is this correct or do shear connectors and clips always have to be purchased separately?