How do I fit a drain gully when the drain pipe is very close to the surface?

Question

I wish to lower some paving round my house, as it is too close to the DPC (damp-proof course). However the drain pipe will not be very far under the new level of the new paving. Therefore how can I fit a drain gully when the outlet pipe is only a few inches below the top of the gully?

(All the gullies I have seen has the pipe outlet near their bottoms, rather than near their tops.)

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This is what I mean by a drain gully.

The is the problem.

The problem I have is that the current level of the drain pipe (in the ground) is about the same as the level I need the top of the Gully hopper to be.

Answer 1

Given that the water will only drain as low as the bottom of the drain pipe, you may have to put in a new drain pipe, or move the existing pipe so it's deeper. If you're lucky, it has a steep runoff angle so you may only need to replace/move a few feet of it to get it to a better depth.

Beyond that, you can buy the gully hopper and build your own u trap, allowing the exit to be placed as high or low as needed. Ideally it'll be several inches below the top of the gully, but it may be sufficient to have only an inch or two.

However, drainage away from the house is extraordinarily important, and if you're going to the trouble of lowering the paving, you should consider adjusting the drain pipe so the slopes and depths are correct for the new position of the gully.

Answer 2

If I'm reading your question right, you need to know if the new gully level will be deep enough to handle all of the water that will be flowing into it. I assume the drain pipe you're talking about is one coming off your downspouts and gutters. So the total amount of water would be water from the roof, and any water that gets drained into the gully from the walk.

Unless you live in a place with constant heavy rains, a few inches should be able to handle that much water. Also, when you dig up all the pavers to lower them you could deepen your gully trough at the same time and then just attach a piece of drain pipe to the current one so that it goes lower with the new gully.

If you can't deepen the gully and you think the volume of water will be a problem for the depth of the gully you could install a plastic barrel-style cistern to catch water coming down the roof drain. This will give you free water to water your lawn, and keep water out of the gully (unless you let the cistern get full).

Hope this helps.