Confused over existing drainage construction

[KandR]

Hi

We're trying to battle with a very flooded (6 plus inches over an area approx 3 x 3m) garden, part of which is ours
and part a neighbouring property. (The neighbour is alledging the drain is on our property and hence we are causing the
problem and should fix it.) However we can't work out how the drainage is supposed to work to determine
what the problem is and hence try and resolve it.

We have a manhole at the bottom of the garden. (I've checked the deeds to the property it is not marked on any of the
plans or mentioned in any of the corresponding documents.) Under the manhole is an approximately 6 ft deep pit.
We are on clay soil, hence the pit is effectively clay lined. The manhole is located in the local low point (the best
way I can think of describing it is if you picture a soup bowl the manhole is towards one side and the area floods and
retains water like a bowl). We have dug out and de-silted the hole (several times to no effect). The hole has 3 pipes
heading into it 1 from the direction of our house and 2 from the direction of the neighbours on each side. It then
has a 4th pipe heading out of the pit towards the house behind. (We have been unable to ascertain the slope
angle on this pipe as to whether it slopes into the pit or out of the pit.)

Our neighbour (very elderley and confused) sent round a drainage contractor last night who claims he did some work
on the drain 3 years ago and that it is not a soakaway but a pit with inflow and outflow. He claims he used some
form of flexible pipe (suggesting 35 metres length of) to unblock what he calls the outflow pipe, and as we haven't been
maintaining and doing this we are causing the problem and should arrange for someone to clear the outflow pipe.

We are reluctant to do this as if he only cleared it 3 years ago, we've owned the property for 2 years and it's flooded
for 1 year, then he doesn't seem to be offering a very permanent solution to the problem.

Have you ever heard of such a drainage construction? (it's a Jones Homes property built in the late 1960s) Any ideas
how it is supposed to work? E.g. common sense would say why have the pit and the gap in the pipe to allow them to silt up,
why not just build a continuous pipe? And where might the outflow outflow to?

Any help would be very gratefully received. Alternatively can anyone recommend a reliable / experienced drainage
consultant in the Macclesfield, Cheshire area who can help us?

Best regards

[matt h]

It would seem that you do have an inflow /out flow pit, and unfortunately for you the out flow appears to be blocked. It would require rodding, and ass this is a recurrent problem, there may be a pipe collapse somewhere along the line. I N THE SHORT TERM i WOULD TRY RODDING THE HIGHEST HOLE IN THE PIT, WHICH IS NORMALLY THE OUTFLOW. I would however advise that you get a drainage engineer to check your drains with a camera, to find out the extent of the damage. Check your insurance policy to see if you have adrquate cover for this

[matt h]

Take a look at the main site under drainage, the different types are explained in glorious detail, so you will perhaps understand how this type of drain is supposed to work... Pervious pipe drains as i call them do have inherent problems and do require maintenance. I f the drain is on your property you are unfortunately liable for its maintenance. See section about dye testing for flow of drains, it may help with layout and fall diagnosis

[seanandruby]

it sounds like a catchpit. is the base solid? the base should be approx 300ml below the lowest invert. is there what looks like a pipe on top of a pipe going out? it could be an interceptor. if not then you almost certainly have a blocked, or collapsed pipe. have you tried rodding the pipe? you have to find the next manhole, it should be within 90 metres.

[matt h]

if you have found the next man hole, lift the lid and rod back towards yr pipe, that is if its clear... I f the manhole is outside your boundary, then its your local waterboards problem. Have you found the outlet of the pipe yet?

[KandR]

Thank you all for your advice. The base is just the clay soil of the land in this area. There are drain rings which go so far down, then it effectively just turns to a mud / clay hole. But yes the base is below the pipes and it does look like the pictures Matt H referred us to. Tried scouring the area for the next manhole but with little success. Had a professional out for a look and he suggests jetting the drains then using a sonar tracer to try and locate any blockage...we are still awaiting his quote but it is a tempting option as at least then we would understand what we're dealing with for any future maintenance. Also as the manhole is right on the edge of our property 3 of the 4 pipes are on other peoples land and our insurance will only cover pipes on our land, so we may need an experts report to get any problem we find fixed.

[matt h]

unfortunately such is the problem with shared drains.

[seanandruby]

if there is no concrete base then it is a soak away. sounds like its silted up. may need sucking out.could be the pipes are all inlets. from filter drains, that's why there's no other manholes. you certainly need to find out if the contractor put in an outlet, or bodged it. has there been any digging locally? the gas, electric and any other service suppliers are renowned for smashing pipework and not replacing it. done a few repairs where this has occurred, even on fowl runs.