How To Size A Sewage Treatment Plant

The below guide will take you through the process of sizing a sewage treatment plant:

Step one: Find out how many people the property can accommodate.

British water flows and loads 4 document states that:

A property of 3 bedrooms must be sized at 5 people.

A property of 4 bedrooms must be sized at 6 people.

A property of 5 bedrooms must be sized at 7 people

A property of 6 bedrooms must be sized at 8 people

Multiple properties are sized individually and added together. From 13-25 population you can reduce the figure by multiplying the population by 0.9. From 26-50 population you can reduce the figure by multiplying by 0.8.

Example A:

4 bedrooms = 6 people

Example B:

5 bedroom + 6 bedroom property = 7 people + 8 people = 15 people.
Then multiply by 0.9 & round up: 15 x 0.9 = 13.5 (14 rounded up)

Step 2: Tank the population and round up to the nearest sewage treatment plant.

All UK treatment plants for domestic use are rated in their maximum population equivalent (PE), there are many different makes and models all using various styles of treatment and made from different materials. Some are noisy, some are silent. Most cheap sewage treatment plants will use budget air blowers which won’t last as long and will be noisier than more expensive alternatives. A more expensive model will normally contain a higher quality of components and be engineered to a better degree.

In the long term this normally results in less failures, call outs and a cheaper lifecycle cost.

You can download the latest version of the British Water Flows and Loads document below: