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What Septic tank size for my house?

For a FREE quotation for any Septic Tank, Sewage Treatment Plant or Soakaway, replacement or installation, get in contact with us on 0800 3101092 or via our contact form.

What Septic tank size for my house?

If you are thinking of installing a new septic tank at your property then it is important to know how big the tank needs to be. Even if you are having a professional company installing the tank it is good to know the basics.

Firstly if you are considering installing a Septic Tank it would be worth also reading our article on septic tanks versus sewage treatment plants. As a one-liner, if you want to discharge your effluent to a drainage ditch or watercourse then legally it will have to be a sewage treatment plant. Further because of the need to have a secondary treatment in the form of a drainage field the installation is likely to be more expensive than that of sewage treatment plant system.  

Okay so it is definitely a Septic Tank you want, your next job is to work out what kind of septic tank it is you are after. Read our article which type of Septic Tank should I buy. We recommend the Graf injection moulded plastic tanks.

Okay, so building regulations are very clear on how big the septic needs to be. This is detailed in Building regulations 2010 H2. The minimum size of the Septic Tank is 2,700 litres (2.7m3 ) for up to 4 users. For every additional user this should be increased by 180 litres. The problem is how many people do you count?

What happens if your septic tank is too small?

The trick is that obviously you don’t want to have a party or family over for a weekend and then your toilets backup because your tank is not big enough so it is recommended you build an element of leeway into the guidance set out.

Can your Septic tank be too big?

If you go for a ridiculously large tank for two people than you will pay more for the installation as the hole needs to be bigger and also the amount of aggregates, cement, sand etc you will need. Will it affect how the tank will work, probably not but it might get very smelly.

Okay, so how big should my Septic tank be?

We like to use the Graf carat septic tanks, they are really good quality and easy to install. We would recommend that for a normal size house 3 to 5 bedroom go for the 3,750 litre tank which caters to a maximum population of 11. If you have a country estate, then firstly hats off to you, you should go for a 4,800 litre tank which caters for up to 18 people.

As you can see there is no exact science as to how big a Septic Tank should be. When speaking to tank manufacturers they are increasingly adopting the British Water Flows and Loads guide that is used to size Sewage Treatment Plants. Per the regulations relating to Septic Tanks, we would advise that this will leave you undersized.  Please see our article relating to What sewage treatment plant size for my house? If you are considering installing a new septic tank please get in touch and we can help. We offer free quotes for all installations.

In reality, I think because of the economics and legal environment a sewage treatment plant is normally the better choice. It is, of course, personal preference and this is not definitive I would just say you should consider both

Want to learn more?

We have a large collection of articles containing the answer to all of your questions. Check out our Blog Page 

Our Core Services: The Sewage Treatment expert Installers

On the 1st January 2020, all Septic Tanks that discharge to a Stream, Watercourse or Drainage Ditch will become illegal and will require replacing with a Sewage Treatment Plant. Please see here for more details.

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Expert wastewater treatment engineers who specialise in Septic Tank and Soakaway replacements as well as Sewage Treatment Installations. We are based in the New Forest, Hampshire but operate across the South Coast as well as Wiltshire, Somerset, Devon, Sussex, Surrey, Oxfordshire, and Berkshire.

The Home of Septic tank and private drainage system solutions. 

Based in the New Forest, Hampshire on the border with Dorset and Wiltshire we operate an expert team of off-mains drainage specialists. This encompasses Septic Tank, Soakaway and drainage system problems, installations, blockages, and servicing. In addition, any issues relating to cesspits and sewage treatment plants.

Homeseptic offers high quality, professional advice, repairs and installation for all aspects of effluent cleansing and disposal across the south of England. Whether you’re looking for septic tank installation, sewerage treatment plants or systems, piping or soakaway solutions, Homeseptic employs only the most competent engineers in the drainage and treatment industry and knows exactly which solutions suit each property.

We only install and offer quality systems we believe in, from suppliers we know and trust.

New Forest Philosophy

As we have said Homeseptic is based in the New Forest. A great location in between the cities of Southampton, Salisbury and Bournemouth. We are a group of good friends who grew up together in the area.  Individually we all have grown tired of the way other Drainage firms are run. As a result, this is why we set up Homeseptic.

We want to actually put the customer first and turn up to do a great job that we can be proud of. Unfortunately, this is not the case in the market, with most companies pressuring their workers to sell unnecessary works on a visit. Due to this, we offer upfront quotations with any variations discussed before we start work.

We are honest hard working professionals, which we hope you will agree with. As a result, it will certainly not turn up in flash sales vehicles and give you a load of chat and then do a terrible job. Our team will come with the job in mind and the aim of giving you the best value we can in order to facilitate a quality installation. 

We cover all of Hampshire, West Sussex, Dorset, Somerset, and Wiltshire. Please get in touch and see what you think.

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What Septic tank size for my house?
If you are thinking of installing a new septic tank at your property then it is important to know how big the tank needs to be. Even if you are having a professional company installing the tank it is good to know the basics.
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