Installing channel drainage on patio.

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Hi All

We inherited a raised patio when we bought this property. It's surfaced with those big old 3'x2' concrete flags and has a low point in the middle where water tends to stand after heavy rain. Its not so much of a problem in the spring and summer, but in the winter when the rain is more persistent and the water table rises it can take days rather than hours to drain away.

It strikes me that rather than taking up these very heavy flags and resetting them to create a fall, it would be easier to install channel drainage at this point to take the water away. Something like this:

https://www.plastics-express.co.uk/...em/aqua-hdpe-drainage-channel-x-1m-p-kdc307aq

Couple of questions prior to installation. I intend to cut the channel with the flags in situ rather raising them, due to their significant weight (I have a dodgy back). First, are these things designed to fit together or do you need to buy connectors? Second, do they need to be set in concrete for stability or would it be OK for them to be laid on the clay subsoil?

The plan is to attach 110mm pipe to the end of the channel via an outlet and drain the water onto a lower part of the garden.

The garden is heavy clay, hence over the last few years I've had to address numerous drainage issues, but this is the only part of the garden where I still have a problem, albeit a fairly minor one.

Any advice welcome, thanks.
 
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Sounds good, we had a run of those channels and they just slotted together sitting on the soil. You'd only need concrete bedding if you wanted to drive on it. Just sharp sand and chuck in a little cement if you're worried.
Paving expert web site is an excellent resource, saved us thousands.
Being honest you might be able to do something low tech, even angle grinder to make a groove and let the water away might be enough. Any photos?
 
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Thanks, John.

Yes, I've browsed Pavingexpert many a time for drainage and paving related topics and its very useful, as you say.

The patio is covered in snow at the moment, but when it clears I can take some pics.

TBH the problem has been exacerbated by the fact that I installed a pond next to the patio in the summer, but neglected to consider the likely effects of the high water table. There's been a lot of hail and rain recently, the ground is waterlogged and the centre of the liner has lifted, which has caused even more flooding.

I suppose I could cut a groove, maybe fill it with stone and see whether that does the trick. If that didn't work, then I could cut a wider groove and fit the channels. Can't do much in this weather anyhow.

Thanks again for the response.
 
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Yes just for the record the channels are more for relatively high volume of water quickly leaving a level surface, you just want t rido of it within a reasonable time.
 
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It definitely doesn't tend to be a significant volume of water that needs to be shifted, and its more annoying than disruptive. I suppose the problem has taken on an extra and temporary significance recently, what with days of hail, rain and now snow and now the added problem of the lifting pond liner.

So yes, I'll probably try the "stone filled groove" approach and see whether that does the trick.
 
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Aco drains butt together, however they need to be laid on a concrete bed. We lay a dry-ish concrete bed then use mortar for fine tuning. They also require a wee bit of haunching up each side. Take up the slab or you will regret the fact that you will be tunneling beneath them and then be totally fed up that they are wobbling about after all the efforts of sustained abuse going on and around them.

Surely taking water anywhere other than into a drain is going to cause problems with a clay substrate?
 
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Thanks for that. You're right about the clay substrate, although prior to my installing the pond whatever standing water remained on the patio was usually gone within the hour after the rain stopped, having seeped through the joints between flags into the soil/ clay below.

What's been happening recently is that the pond liner is lifting as the water table rises after heavy and prolonged rain and the pond is overflowing onto the patio, adding to that historical problem with standing rainwater. This amount of water is taking much longer to clear. There is a soakaway at a lower point in the garden which could take most of that additional water, but only time would tell whether a land drain is needed as well.

Obviously, the substrate below the patio has been capable of dealing with rainwater but that overspill from the pond is exacerbating and prolonging the problem. Removing water from the pond to reduce the level only seems to encourage the water table to rise further, to lift the liner again and create more flooding.

So its a choice between three options: cut a groove and hope that deals with the excess water, cut and install channels and know that it will but that this may create a problem elsewhere, or move the pond to a higher point in the garden and just put up with the standing rainwater, which as said above is usually gone fairly quickly.
 
D

Doggit

I know you can't take pictures at the minute, so we can't give absolute advice yet. You've got a dip in the patio, so can you find a straight and flat point for the channel to go in, that will also allow you to set in the pipe to take away the water to the soakaway. What you don't want, is the channel to go down, and then upwards. The will have a exit point at the end of them that will connect to a down pipe rather than a 110 soil pipe. But if you've got a raised patio, then has it been raised to point where you also need to fit it around the house, and stop any bridging of the DPC, or is this level okay. If you have to take it around the house, then could you branch it out to the dip, and then get the whole lot drained out to the dsurface drain.
 
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Thanks once more. The snow has gone and by tomorrow I should be able to take pics.

The raised patio is separated from the house by a path at a lower level which runs along the back of the property and which incorporates its own drainage channel. The area into which the patio currently drains is a gravel-filled soakaway which I installed by digging out an area of clay, and which was originally intended to take normal drainage from the patio before the pond was installed.

I'm hoping this can cope with the pond overflow as well without the need to dig land drains.
 
D

Doggit

Sorry amfisted, but you'll need to redig the soakaway, and install soakaway void crates instead of gravel. This will then handle the overflow problem much better, and may even stop the ground swelling. But have you gone down sufficiently to allow the water to permeate into normal ground. If you haven't, then the water will go into the soakaway, and just sit there.

What's the soakaway for, and how do you get the water into it, and where is the water that goes into it coming from.

When you do the pictures, put a straight level on the ground to show the fall/dip please, and a few pictures around the house, to show the drains etc.
 
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I did originally install a soakaway crate but clearly didn't go down far enough to breach the clay substrate, and the crate became an underground plastic swimming pool overnight. I reckon the clay is a metre deep at least, and at my age I'm not sure that I'm capable of digging that out!

I originally put the crate in during the winter of 2015/16, when here in North Wales we had two months of almost constant rain and the ground became totally waterlogged. When the crate didn't work I waited till the ground dried out, then dug the soakaway and filled it with gravel. It's an area about two feet deep by two feet wide by six feet long, and it copes with normal rainfall. However, the problem has been exacerbated by the overflowing pond, so unless I move the pond as mentioned above, I need to do more.

The area which is now the soakaway was originally heavy clay before I dug it out to the dimensions above, and the water drains into it from the patio by spilling over the edge of a retaining wall which is constructed of largely unbonded bricks, stones and blocks.

Pics to follow tomorrow, with luck.
 
D

Doggit

The crates will handle a lot more water than gravel will, but the drawback is they are much more expensive than gravel. If you've got down to soil, then having the crates in that soakaway, may well solve all your problems.
 
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You're right, they are expensive. I can't remember exactly how much the original order was, but I didn't get much change out of fifty quid for one crate, the fabric to wrap it in plus securing tape. Can't justify spending twice that right now on a problem which is still only occasional, especially when I can usually brush the water off the patio into my waterlogged soakaway if the worst comes to the worst.

However, I'll revisit the issue in the New Year subject to weather and paydays. Best get some painkillers for my back in preparation for all that digging. ;0)

Thanks again.
 
D

Doggit

Have you thought about using milk crates in addition to the one you've got.
 
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Unfortunately, the one I have has been dismantled and the sections have been used as ground reinforcement for an area where I store firewood, so I'd be starting from scratch. However no, I hadn't thought of milk crates. Are they likely to be as sturdy as the real thing?
I don't think I've actually clapped eyes on a milk crate for years!
 

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