When it comes to septic tanks, size is everything. A septic tank is used where there is no connection to the sewage system and enables water to be discharged through the ground via a soakaway system. The dimensions of a septic tank are therefore key to ensuring that it conforms with building regulations and works in the long term.
Too small a tank and you will need to empty it more frequently, otherwise it will almost definitely lead to slow drainage, sewage backups and internal system failures and worst-case scenario, environmental damage from contaminated water leaking into the ground.
So, while you may think you’re saving money by scaling down tank size, it is actually less cost effective. Best at the outset to learn how to size a septic tank so that you know exactly which capacity is right for you.
What size septic tank do I need?
The Environment Agency estimates per capita consumption of water to be around 150 litres per day but remember this is an average. Some households will use more – maybe they’ll shower more frequently, or have small children and have the washing machine on constantly – so when you are doing a septic tank size calculation you need to overestimate water usage.
Firstly, you need to work out how many people the property accommodates. The UK Gov website has a septic tank size calculator specifically designed to help you calculate the septic tanks size you require for your property. www.gov.uk/government/publications/sewage-discharges-calculator-for-domestic-properties
Here are the basic guidelines:
Septic tank size is usually based on the predicted daily flow rate.
A common rule is to have a tank capacity of at least 2.5 to 3 times the daily flow rate. This allows for adequate settlement and digestion of solids.
- A single property of up to 3 bedrooms must be sized at 5 people.
- A single property of 4 bedrooms must be sized at 6 people.
- A single property of 5 bedrooms must be sized at 7 people
- A single property of 6 bedrooms must be sized at 8 people
- Multiple properties are sized individually and then added together.
You can also find out more information at British water www.britishwater.co.uk
The things to look for in a septic tank are the materials and drainage system used, capacity, hydraulic capacity matched to property size, projected flows based on how many people live in the building and headroom for future expansion – i.e. you need to determine what your future needs will be not just the existing set up. Will you be adding more bathrooms, expanding your kitchen or the number of people in your household?
In England, any home installing a new system discharging to ground or surface water must comply with the legals outlined here:
www.gov.uk/permits-you-need-for-septic-tanks/you-have-a-septic-tank-or-small-sewage-treatment-plant
If you do not follow the rules the Environmental Agency will step in to offer advice and if this is not heeded, they will take enforcement action against you.
As you can see, there’s a lot more to septic tank installation than you might think, which is why you should call in the professionals at Yorkshire Septics. We’ll work out the best tank for your needs and will take into account your budget constraints. Just follow the link below for more information.