For gardens, it's usually recommended that pipes have at least 450mm of cover. As for size of sump, that will depend on just how effectively it can be pumped clear. The trouble is that, as you drain your garden and store it in the sump, the groundwater in the surrounding land will most likely drain into your garden along the hydrostatic gradient created by the sump, and so, theoretically, you're draining not just your patch of one-third acre, but all the adjacent land, which could be 2, 3 maybe even 5 acres.

You really need to bring in a local drainage consultant to survey the site and advise you accordingly. I can't suggest any guaranteed solution without being familiar with the site, and Somerset is a bit off my patch, unless you can wait for the summer, when we usually have a week-long break with friends in North Devon.

we are puzzled by a drain cover at the higher end of the garden (away from the house). Does anyone have a clue what this might be?

How do we find out whether the water from the roof is draining into this?

You can also buy special drain tracing dye from builders' merchants that do the same thing.

Who do I approach to advise me locally regarding necessary drainage for the garden without leaving it dry and hard in the summer? Is this something I am likely to be able to figure out myself.

The perforated pipe is probably the best solution, but you need to have somewhere to where these pipes can outfall, such as a sewer system, preferably a surface water system, or a ditch, stream etc. I doubt that a soakaway is going to be feasible given the conditions you report.

Terram is a brand name for a range of geo-membranes and drainage composites. The primary use for the Terram geo-membrane in the land-drainage business is to line land-drain trenches in order to prevent infiltration of small particles of silt, clay, etc. that can clog the system. The drainage composites are used for fin-drains and are being used successfully on commercial drainage schemes, but I've never used them on a residential scheme; I suspect the price would be prohibitive.

In your situation, I would look at using an 80mm dia perforated flexible plastic pipe, as described in the land drainage section of this site. It's cheap, simple to install, and highly effective.

Now, if you introduce a pipe that has a big empty space in the middle of it, the water will flow into that space, thereby reducing the hydrostatic pressure in the surrounding material. It doesn't escape out of the pipe through the perforations because the hydrostatic pressure on the outside is still greater than that within the pipe, and so any water acquired by the pipe will flow, under gravity, along the pipe to some point of outfall.

It's all simple physics, really.

from what you've told me, I would suggest using an interceptor/collector drain at the boundary of the property, and have it outfall to a ditch safely away from the garden. Depending on the exact site conditions, a fin drain might also be suitable. Have a look at the drainage section of the site for more info on both these types of drain, and let me know if you need more info.

Depending on local conditions and the amount of work to be done, a collector drain normally costs between 8-15 quid per linear metre installed when less than a metre in depth.

You don't sound terribly confidant with the contractor you've called in. You should always get at least 3 quotes for any work of the nature; if the contractor know there is only them up for the job, you run the very real risk of being ripped off! Get at least 2 more quotes before giving anyone the go-ahead to proceed with the work.

A BCO would have you take the lot out!

A water table can be very shallow, but, with me living in the big metropolis of Warrington, I'm not familiar with this liitle village you mention (Lundun, did you say?), so I can't say exactly what you should expect, but I wouldn't anticipate such a dramatic change in level over such a short distance.

Could there be a leaky water service nearby?

If that doesn't help, post back here and I'll see what else I can do.

Your man is trying to rip you off!

Whereabouts in Manchester? Contact me by email, and I'll see if I can put you on to someone who might be able to help.

Anyway, when you say the nearest "drain" is approx 2' higher than the low point on the driveway, do you mean the cover of the drain or the invert level?

Pumping water uphill is a bloody expensive business. You'd need a sump chamber, with a pump and a float switch, plus a rising sewer to pump the water along until it reaches the main surface water system, then a trap to prevent the SW system surcharging into your sump....it really has to be a last resort. Is there no other drain point nearby, even if it's on a neighbours' property or even in the carriageway?

Can a builder reasonably ignore this problem ?

Are there any regulations covering this situation or, what is recognised good practise that can be expected?

Whose responsibility is it?

What would you advise is the best method to deal with the drainage?

Whereabouts are you, Gordon? There are some good salvage yards up here in NW England.

Good luck! Let me know how you get on.

Have any percolation tests been done, or do you know for a fact that the sub-soil is very free draining, Guy?

If you have existing drainage, I'd tap into that, as then you know the water will be drained away and not left hanging on the paving. Cost-wise, a proper drainage connection wouldn't/shouldn't be much more than the cost of a French Drain. 50 quid or so for a connection, pipework is around 20-25 quid per metre and a linear drain can be bought for around 10 quid per linear metre. Ask your contractor to price it as an option - there's no harm in asking.

I don't understand - why would a dpc have any connection with a plastic IC? You only have a dpc in the brickwork of the house walls - why do you think it would be a problem with a new IC?

If you are planning to incorporate a drainage IC within an internal floor, first, you must have the drainage plans approved by your local Building Control Officer and second, you will need to use a double-seal IC cover to prevent any gases or odours arising from the sewers.

The dpm is laid up and around the IC, trimmed to suit. It's not critical if it just touches the sides of the chamber, or if it comes, say, 50mm up the sides. The purpose of a dpm is two-fold - to prevent the concrete being dried out by the sub-base and to protect the concrete from any 'corrosion' from beneath. A gap of 25mm or so around an IC is not the end of the world.

There are two types of interceptor that you could consider - a surface interceptor, and a sub-surface type. The sub-surface type is normally used when there are problems with groundwater draining into an area, but you neighbour's concern seems to be regarding the surface water, so I'd opt for a surface interceptor.

The two simplest types of surface interceptors are Dished Channels, as illustrated on the Road kerbs page or the Linear Drains described in the Drainage section of the site.

Lay these on a concrete bed and haunch, as shown, and connect to the nearest SW drainage point, which will probably be a gully or rainwater pick-up. Dished channels, of the decorative type, cost around a tenner per linear metre, and you can get a cheap linear drain for that sort of price from B&Q or HomeBase.

The Environment Agency have a special team to deal with 'over anxious' callers who plague them with complaints about impending disaster only to find the lake on a neighbouring property is actually a bird bath, and the industrial extraction unit is a kitchen Xpelair!  

I'd be tempted to saw through the downspout 100-150mm or so above ground level just to see if the downspout is blocked solid or whether it's just blocked at the top end, where the gutter hopper is. Then, if it's not as bad as you think, the downspout can be jointed back together with a coupling (if you can find one for that range of above ground pipework) once you've cleared the obstruction. Alternatively, use a shoe and discharge into a Hopper or Gully (see below)

However, if the blockage is below ground, causing the detritus to back-up, then you're going to have to dig down and follow the pipework until you find the cause and then fix that according to what you find. If it's just silting-up through years of use, you may be better off replacing the entire pipe run rather than trying to salvage what's there. If it's a broken/collapsed pipe, you might be able to repair. If the soakaway itself is choked.....uh-oh! Time to start again.

Whatever the cause, you might as well take preventative measures to avoid this happening again in a few years time. Fit a litter trap into the hopper of the guttering to keep out leaves and mosses. Consider fitting a P-trap and hopper or a yard gully at the foot of the downspout to act as a catch-pit for any bulky crap before it gets to the soakaway, rather than piping straight through, and, if you do end up having to re-pipe the drain, incorporate a rodding eye or access chamber so you can get at the underground pipes without having to dig everything up.

I can't tell you how deep the soakaway will be, or how far the downspout will travel beneath ground level before it meets the drainage system, as each situation is unique and there are no set standards. I can tell you though, that discharging onto a flower bed is a very, very last resort. If the roof area being drained is greater than 10m², I wouldn't even consider it unless the house was built on sand/gravel and know to have excellent groundwater drainage.

Let me know what you find.

the usual remedy for this sort of problem is to cut a channel in the concrete slab and install either a linear drain or some form of kerb channel, such as the Keychannel by Marshalls, and direct that to the nearest gully.

You'll need a Power Saw to cut through the concrete, and the linear drain or channels will need to be bedded on concrete or mortar to a level of around 3mm below the concrete surface. You can then patch in around the newly installed drain/channel with fresh concrete or a grano mix.

HTH

You need to intercept the groundwater before it reaches the foot of the driveway. This can be done by use of an interceptor or fin drain (see land drainage section of this site), or via a drainage composite. These must then discharge into the existing drainage system - you cannot rely on a soakaway, given the existing ground problems.

Once the drainage is sorted out, you'll have no problem installing and maintaining a block paved driveway, and you should have no further problems with your neighbours.

Have you spoken to any local contractors about your plans? The site needs to be investigated before the most appropriate remedy can be designed and implemented.

If the outfall of the drainage pipe is submerged, then it will affect its ability to drain - in effect, the water in the ditch will surcharge into the pipe and travel towards your land.

When you pump out your catch pit, where do you pump the water to? Into the Foul System?

When it comes to building a bigger storage reservoir, you'd really need to understand the local hydrology. You could end up providing spare capacity for all your neighbours and the ditch, while not gaining any benefit for yourself. A pumped storage facility, what we call a wet well, discharging into the FW system may need a consent from your local authority, just depending on what the local flood plan is.

A one-way valve or penstock on you discharge pipe may be a simpler answer. Have you spoken to any local drainage contractors?

Let me know how you get on.