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Basement foul waste.
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It is assumed that waste from a toilet, shower, steam room, small kitchen, plant room etc. will just flow down and go away as it does from your main bathroom and main kitchen on the ground floor.
But your basement is already deeper than your sewer that discharges into the system under the road.
Your foul waste from your basement needs pumping up to discharge into your sewer or other arrangement such as a tank under the garden.
The purpose of this page is to sew the seed in your mind that if you dig your basement another 2m deeper to put a big tank under the basement floor from which to pump foul waste up to your sewer occasionally, that the civil engineering difficulties and costs of excavating a total of 5.5m down from ground level could be considerable.
If you look carefully at the bottom of the image to the right, that is a digger digging deeper. The hole is supported by about £30,000 of temporary works piling and frame.
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It is often not appreciated, particularly by architects, that building site insurance policies normally limit cover to 3m deep only.
If your architect specifies a sump beneath the basement floor slab, the most risky and dangerous part of your basement construction will be without any public liability insurance, without any employees' liability insurance, without any insurance at all.
Are you prepared to accept those risks out of your own pocket?
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I just want you to think that foul waste from a basement might be unnecessary or perhaps the pump needn't be so deep.
Obviously the pump in the white box beside the washing machine will be boxed in to look nicer, but that's all that's needed if every source of foul waste has its own Saniflo-type macerator pump.
The cost-saving is immense.
But, my warnings don't stop there.
The pump sump might leak or there might be a leak around it.
This has both.
A hole about 10mm diameter seems to have been drilled down through the centre. Probably to let water in when they were trying to get it to stay in position below the water table.
The water pressure from underneath was so great, it cost about £500 to fix that little hole.
You have to remove debris, remove water, and clean up before you can see what you have to do next. It takes ages.
When almost all other sources of water were eliminated, only then did it become clear that the water pressure in the ground beneath was so great it was getting past the plastic collar of the sump.
The difficulty now, is how do you chisel out concrete as hard as rock while leaving and not damaging a thin and flexible bit of plastic, to enable a repair?
Knowing that as you remove concrete the water will increase. You will be flooded. The pump will block with sand. where does it stop?
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