Drainage - Typical Schemes

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Drainage Schemes

Medical Centre

The drainage scheme below shows a typical layout of a separate drainage system.

The building is a two-storey medical centre.

Can you identify the various drains and fittings?

The drawing below shows the previous drainage scheme with some details added.

Nursing Home

The drawing below shows the plan of a single storey Nursing Home.

There are two separate buildings.

The yellow circles indicate foul water pipes exiting the building through the floor.

The pink squares show roof downpipes and gullies from the surface water drainage system.

The drawing below shows the proposed foul water below ground pipe layout.

It may be possible to reduce the number of manholes i.e. No.6 and No.7 could be combined.

The next step would be to size all pipework between manholes.

Then pipe gradients, manhole depths and invert levels could be calculated if surface levels were known.

When you examine the above drawing you will notice that there are a large number of 100mm diameter underground pipes from sanitary appliances to manholes.

It may be possible to reduce the number of these underground pipes and have fewer connections to manholes.

This can be achieved by a variety of methods as follows;

1. Join some sanitary appliances drainage pipework above ground outside as shown below.

This method is not as neat as when all pipes are underground but the important aspect of access is achieved with the cleaning eye.

2. Join some sanitary appliances drainage pipework above ground inside as shown below.

This method has the advantage that footpaths outside are not obstructed.

Sizing Main Foul Water Sewer

Appliance	No. off	Discharge Units each Type of application Public	Total Discharge units
Basin	5	3	15
Bath	2	12	24
Sink (large)	2	8	16
WC (9.0 litre)	5	10	50
Bidet	2	8	16
Washing Machine	1	8	8
Shower	5	8	40
Dishwasher	1	8	8

TOTAL = 177

From graph 150 mm pipe is suitable.

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Drainage - Typical Schemes