septic tanks
Septic tank size
- Septic tank
- Sewage treatment plant
- Cesspool
- Non-standard system such as reed bed
In any such case, you, as the homeowner, are responsible for meeting the general binding rules.
To make sure your septic tank works as it is designed to, it needs to be capable of handling the flow of effluent that your premise is producing.
How to determine septic tank size?
Step 1: Determine “P” (Minimum Population) from the number of bedrooms you have
The volume of effluent coming from your house is determined by the number of people using the system. This is calculated based on the number of bedrooms in your home.
*Reference: Flows & Loads from British Water
**Please note that the abbreviation for Minimum Population is “P”
Small one and two-bedroom houses or flats
- Flat with one bedroom = minimum 3P system
- Flat with two bedrooms = minimum 4P system
Single house – up to and including three bedrooms: P = 5, add 1 P for each bedroom thereafter.
- House with three bedrooms = minimum 5P system
- House with four bedrooms = minimum 6P system (5+1)
- House with five bedrooms = minimum 7P system (5+2)
- House with six bedrooms = minimum 8P system (5+3)
*Reference: Flows & loads from British Water for larger domestic housing, commercial and industrial premises.
Step 2: Calculate the number of litres of wastewater produced per day
British Water estimates that one person creates 150L per day. To calculate the number of litres per day for your property, just multiply the number of people x 150L.
Example: three bedrooms house = 5P (see step 1)
5 P x 150L = 750L per day
Step 3: Add 2,000L to your litres produced per day
Carrying on with the example above: 750L (step 2) + 2,000L = 2,750L
Therefore, the minimum size septic tank required for this example is 2,750L. For more information on our septic tanks or on our wastewater treatment solutions, do not hesitate to download our ebooks.
Choosing the correct size septic tank
Given the choice, it’s recommended to round up the tank size required. If a septic tank is too small, your soakaway system will suffer as a result. If insufficient settlement time occurs, small suspended solids might block your soakaway. In which case, you will have to replace it or convert it to a new sewage treatment unit.
Use our Septic Tank calculator below to define the one you need:
| Number of bedrooms | P | Minimum size of a septic tank | Tricel recommendation |
|---|---|---|---|
| 1 | 3 | 2450 | Tricel Vento 6 |
| 2 | 4 | 2600 | Tricel Vento 6 |
| 3 | 5 | 2750 | Tricel Vento 6 |
| 4 | 6 | 2900 | Tricel Vento 6 |
| 5 | 7 | 3050 | Tricel Vento 12 |
| 6 | 8 | 3200 | Tricel Vento 12 |
| 7 | 9 | 3350 | Tricel Vento 12 |
| 8 | 10 | 3500 | Tricel Vento 12 |
| 9 | 11 | 3650 | Tricel Vento 12 |
| 10 | 12 | 3800 | Tricel Vento 12 |
For P greater than 12, please refer to the flows & loads from British Water.
For larger projects, Tricel Vento 20 is also available. Contact us to find out more.
Regulation of septic tanks
Contact us to discuss your project or if you’re thinking of upgrading with a brand new septic tank or switch to a sewage treatment plant.
Visit our Virtual Showroom to interact with our 3D Vento today!
Frequently Asked Questions
You’ll find below some of the most commonly asked questions regarding sewage treatment systems.
Is it possible for more than one house to share a wastewater treatment plant?
Yes, Tricel offers a range of different plants for different options. However, you will need to discuss this with your local council.
I need to replace my septic tank that is compliant with the new regulations... What do I need ? Where do I start?
Please refer to our articles about the UK legislation & the 2020 regulations, Regulations in England & Wales and the homeowners responsibilities.
You can also download our ebook.
Finally, our team is there to answer your questions, discuss your project, and do site visits.CONTACT US
What guarantee do you offer?
Tricel products are manufactured from GRP by its nature is a non-corrosive material ensuring strength and longevity. All metals used in constructing the tank are stainless steel. Electrical and electro-mechanical equipment is guaranteed for a period of one year. Plant equipment and components are specifically designed or chosen to work effectively in the Tricel plant and when used correctly will provide a long lifespan. The guarantee commences from the date of purchase.
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Get in touch
Tricel Environment UK
A trading brand of Dewey Waters Ltd.,
Tricel Weston, Winterstoke Road, Weston-super-Mare, BS24 9AN, United Kingdom.
Tel: +44 (0)1934 422 311