‘Off Mains’ Drainage: What are your options?

‘Off Mains’ Drainage: What are your options?

Over a million properties across rural areas of the UK cannot connect to the main sewerage infrastructure. If you’re one of these properties, you may be wondering what options are available to you when it comes to renewing your foul drainage. To help you understand which solution would best suit your needs, we’ve outlined what each option would involve in this guide.

Option 1: Main Sewer Connection

Connection to the main sewer should always be looked at as the first and best option. If this is at all possible, the Environment Agency will expect you to connect. We recommend you start by checking whether this option has been explored and whether it is viable.

Generally you will be expected to connect to the main sewer, regardless of cost, if you are within 30 metres of it. If you are below the mains and cannot achieve a gravity connection, a pumping station that will pump raw sewage to the mains will resolve this.

What is involved?

You will need to apply for approval by contacting the “New Connections” department at your designated sewage provider, at Cotterill Civils we can help you with this. 

Then you would need to engage a contractor to carry out the work for you. This might be the installation of a pumping station and a rising main or a gravity drain connection. Either way this usually involves some section 104 work in the highway, which in turn involves connection fees, road opening notices, traffic management and highway reinstatement.

If you have to cross third party land you will need written permission from the owner and there will be some legal easement work to be undertaken.

Option 2: Sewage Treatment Plant

This is an aerobic process which greatly accelerates the digestion of sewage and produces an environmentally acceptable quality effluent. This in turn allows you to dispose of the effluent rather than having to pay to have it removed from a cesspool.

The treated water from a sewage treatment plant can go into a running water course, a ground water soak away or in some instances a storm drain. You will need one of the above outlets for any sewage treatment plant installation. An electricity supply is required and reasonable access for maintenance.

What is involved?

You will need to register an exemption online with The Environment Agency for small domestic discharges up to 2m3 per day to ground water soak away or 5m3 per day to a running water course. This is free of charge. You will need a permit from the Environment Agency for larger discharges. You may need planning permission and building notice. At Cotterill Civils we can help you with all this.

For a soakaway, the first thing to determine is the soil suitability and porosity. This involves excavating trials holes, filling them with measured amounts of water, then timing the rate of drop. You must also have enough room for a soakaway on your land. You should never allow anyone to construct a soakaway for you if they have not carried out and more importantly, understood a porosity test and its results.

If the porosity test results show favourably, the soakaway should be constructed in accordance with BS 6297:2007 + A1, 2008. Again, we can help you with this.

Option 3: Septic Tank

Slightly cheaper than a sewage treatment plant, this is the next best environmentally friendly option. If you cannot get to the mains, we will ALWAYS look at this option for you first.

Septic tanks only partially treat sewage at the top of the tank, near to oxygen, and discharge effluent of low quality. The process is mainly anaerobic and therefore much slower than a sewage treatment plant.

The by product of anaerobic breakdown is hydrogen sulphide – this is what often causes the noxious smell around a septic tank. Many authorities in the UK & Ireland prohibit their use. There are very few situations that a septic tank is suitable.

A septic tank could be your preferred option if you want to collect sewage from temporary accommodation, such as construction site cabins or mobile homes that will only be in place for 1 or 2 years. Also, some small amenity clubs that are only occupied at weekends could suit a septic tank better than a sewage treatment plant due to the uneven loadings.

What is involved?

The installation of a suitably sized tank with baffles and/or dip pipes and a correctly sized and constructed soakaway. A septic tank relies wholly on a soakaway and soakaways are the single biggest problem we encounter. It cannot be enforced enough how important this is.

Option 4: Cesspool

This is always the last option we consider for you. A cesspool is purely a large holding tank with an inlet only. It offers no treatment at all and the contents have to be regularly removed by a licences waste carrier with a vacuum tanker.

Unlike a sewage treatment plant or septic tank where effluent constantly runs away and can therefore be sized accordingly, a cesspool has to contain everything and will be up to 20 times the physical size and volume.

If you are on a confined site with no access to electricity, watercourse, soakaway or storm drainage, a cesspool could be your only option.

Chemical toilet waste from touring caravans can only be discharged into a cesspool.

What is involved?

The cost of installing a cesspool is high due to its large physical size, large amount of excavated material and associated concrete surround. On most occasions a good contractor will specify excavation support to keep his workforce safe during installationThis does add cost but is the only way to do it safely if there is not the room for the excavation to be stepped or battered. There is no soakaway necessary for a cesspool.

Common misconceptions

As a rule of thumb, most of the water entering the building through your meter will have to be disposed of through the foul drainage system.

It is a common misconception that the above solutions will “magic away” the water. Unfortunately this is not the case, the water, treated or not, still needs to be put back into the environment. Only mains drainage and cesspool options actually remove the water from site to be treated by utility companies. Septic tank and treatment plant outfalls need careful consideration. You have more options with a treatment plant because you can discharge to a water course if you have one available.

Where to go for advice?

We’re one of the UK’s leading providers in pollution control and can provide you with a solution to meet your specific needs and budget. We can provide you with expert advice on the different options available to you.

Please get in contact – 0121 351 3230.

Or click here to find out more.