If your property is unable to connect to the mains sewerage infrastructure, a sewage treatment plant is an ideal choice. It is considered the most cost-effective and environmentally friendly “off mains” drainage option. When it comes to selecting the size and type of the sewage treatment plant, there are a number of things to consider. Here’s a useful guide:
Contents
How does a sewage treatment plant work?
A sewage treatment plant is an underground tank designed to treat incoming effluent to an environmentally acceptable quality. Once the water has been treated, it can legally be discharged to flowing surface waters or in-ground soakaways, following the applicable exemptions or consents.
How to size a sewage treatment plant?
First, determine how many people the property can accommodate. This is not the number of current occupants but the maximum potential occupancy. According to the British Water Flows and Loads document, the following sizes apply:
- 3-bedroom property – size for 5 people
- 4-bedroom property – size for 6 people
- 5-bedroom property – size for 7 people
- 6-bedroom property – size for 8 people
Multiple properties are sized individually and then added together. From 13–25 population, multiply by 0.9. From 26–50 population, multiply by 0.8.
You can view the latest version of the British Water Flows and Loads document here.
Calculation Example
Example A:
5 bedrooms = 7 people
Example B:
4-bedroom + 6-bedroom property = 6 people + 8 people = 14 people.
Then multiply by 0.9 & round up: 14 × 0.9 = 12.6 (13 rounded up)
What is the difference between a pumped and gravity outlet?
Some sewage treatment plants come with a pumped outlet, while others use a gravity outlet. The preferred choice of sewage treatment plant is one with a gravity outlet. However, if your dwelling is on a slope or hill, a pumped outlet will be required. The pump is designed to lift the treated water out of the tank and discharge it into a ditch or stream.
What is a shallow sewage treatment plant?
A sewage treatment plant with a “shallow dig” profile requires a much shallower excavation than standard units. It is ideally suited for sites where hard rock conditions make excavations more difficult, saving both time and cost during installation.
How can we help?
We are specialists in sewage treatment solutions, including sewage treatment plants, septic tanks, cesspools, and sewage pumping stations. With over 25 years of experience in supplying and installing these systems, we can recommend the best options for your site. We also offer full installation packages where needed. Please feel free to contact us for expert advice on 0121 351 3230.
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