Buying a House with a Septic Tank

Many people have concerns when buying a house with a septic tank - and rightly so.

Even properties with existing septic tanks, which have a Consent to Discharge, may now have to replace their sewage systems.

Failed septic tank soakaway

Septic Tanks were the old method of disposing sewage effluent and have been in existence for nearly 150 years. They are composed of 2 components:

Both these components are important, but it is the SOAKAWAY DRAINAGE FIELD that is the most important part of the system and the part most likely to be in trouble and require replacement.

Soakaways are no longer legal for the dispersal of septic tank effluent and soakaway drainfields have a limited lifespan, usually between 5 and 20 years, depending on the type of soil they are constructed in - sandy soils being the best and clay soils being the worst.

Most people looking at buying a house with a septic tank, simply assume that if the soakaway has failed, they can install a new one. This is NOT the case and the vast majority of sites fail the mandatory soakaway drainfield tests.

The rules on the construction of soakaways and drainfields have changed in recent years and this also includes the replacement of existing soakaways. Before the year 2000 AD, soakaways and drainfields were not even part of the Building Regulations, but in 2000 AD, Section H2 was created and this covers the rules and regulations for foul drainage soakaway drainfields.

In order to be certain that you CAN replace the soakaway or drainfield, then your site has to have the following:

  1. Enough land to put a new soakaway drainfield in. All foul water soakaway drainfields must be in a new area of the garden away from any rainwater soakways, not under drives, parking areas or paths and at least 15 metres from any building and 2 metres from a boundary. As the average soakaway drainfield takes up at least 100M², you can see that you need a very big lawn to site a new one.
  2. A water table that NEVER gets to within 2 metres of ground level, even in a wet winter. 60% of sites in the UK fail this Trial Site Assessment Hole test.
  3. The correct type of soil, neither too sandy or too heavy. Another 60% of sites fail these Percolation Tests.
  4. No roofwater
  5. A site that is NOT in a Groundwater Source Protection Zone 1 . These zones were set up recently by the Environment Agency to protect drinking water abstracted from boreholes. If you are in Zone 1, then you cannot have a new soakaway or drainfield.

If you fail either 2, 3 or 4, then you cannot have a replacement soakaway drainfield NO MATTER HOW MUCH LAND YOU HAVE and could end up with a house that has no sanitation possible.

Sometimes, the septic tank discharges into a ditch or stream. This is and always has been illegal and all such systems must be replaced with sewage treatment plants as soon as possible, or immediately, when the house is sold, under the Government General Binding Rules 2015.

Questions to ask when buying a house with a septic tank

1. Does the septic tank system, including the soakaway, comply with the Environment Agency General Binding Rules. If the owner does not know, then you need to get a specialist wastewater site assessment survey, as it could cost thousands to adapt and it might not even be possible. Ring us for details and surveyors in your area.

2. How old is the septic tank? If it is over 25 years old, it may well be coming to the end of its life, depending on the type of septic tank installed. Ring us to discuss if you are serious about buying the property.

3. How many people live in the house now? If the house that you are buying is lived in by only 1 or 2 people and you are a family of 4, then the amount of water passing through the system into the soakaway will be doubled. A soakaway drainfield that is currently coping with the volume may not cope when it doubles and it may 'Back-Up' when your family moves in.

4. Is the septic tank a private one or is it shared? If it is shared, then you need to be aware of any agreements as to the cost sharing of expenses, such as emptying, repairs, etc.

5. Is the septic tank on my land? It is not uncommon to have a septic tank that is situated on land not being sold with your property. If thsi is the case, then you should look carefully at your rights reserved and any wayleaves granted for you to repair, replace or renew any part of the system not on your land.

6. Can I see the emptying records? Septic tanks only need to be emptied once a year. If the tank has been emptied more often, then it suggests that there is something wrong with the drains and/or soakaway system. If it is longer than 12 months, then there is a risk that solids have passed out of the tank and they might have compromised and clogged the soakaway system.

7. When was the septic tank last inspected? This is usually done when the tank is emptied and you can then see any cracks, water seeping in, broken dip-pipes, etc. If it has not been inspected during the previous 12 months, insist on having a specialist septic tank survey before purchase.

Buyer Beware.