Allerton are the premier off mains drainage company covering sales, servicing, commissioning and repairs of all types of septic tanks, sewage treatment plant, sewage pump stations and soakaways.

We will:

  • Save you money.
  • Maintain your compliance with regulators.
  • Help you protect the environment.
  • Extend the life of your system.
  • Delight you.

Contact us and we will be happy to make a site visit free of charge. Or you can simply discuss issues with any of our knowledgable staff in the office.

COVID-19 - Please note that while we are making site visits, we will not enter the house. We would, however, appreciate a bucket of warm water, soap, and a towel to wash our hands. 


Contact our office to buy yours today!

£6 each*

Allerton Ground Water Tube Sketch Plan

The ideal solution for measuring your soakaway (drainage field) water levels.

Allerton Ground Water Tube

Learn more here.

*2 for £10, 3 for £14 (all prices include UK postage but exclude VAT)

Excellent service and attitude from staff

Mr B (Sewage treatment plant service and repair)

Many thanks for your kind and cheerful service

Mrs Potts (Sewage Treatment Plant Service)

A fantastic experience from quote to completion & considerably cheaper than competition

Mr Stokes, Surfleet (ConSept - New Installation)


We do specialised pump stations for awkward situations!

Need something very small, very shallow, or narrow? Need the inlet at the top? We can do that for you! Whatever your unique specification requirements, Allerton can accommodate!

Understanding Septic Tanks


lf we consider septic tanks as a means of treating sewage, accepted measurements show how inefficient they are. Like lead pipes, if they were offered now as a new idea, they would not find acceptance except in certain conditions.


 Let us consider the organic solids in sewage

Raw sewage, i.e., that which comes from the bath, shower, lavatory, dishwasher and washing machine is a complex set of chemicals together with the obvious organic matter.  In fact, it is the organic waste which provides food for the bacteria to help break down the chemicals: washing powders, cleaning materials and shampoos etc. Basically all that we buy in bottles and eventually flush away.

Detergent image for sewage



How well does a Septic Tank cope with all this?

The answer is not very well.

Raw sewage from a typical household is valued as 300 BOD or Biological Oxygen Demand. This is the same as 300 ppm (parts per million).

What comes from a modern GRP septic tank and some of the bigger brick tanks is no better than 200ppm. Clearly the septic tank retains a third of the solids which have to be removed and treated at a sewage works. - A very inefficient system indeed.

The ground is expected to take this dirty grey-black effluent and deal with it.

The fact is it can’t.  Over the years the gravel below the soakaway becomes black with all the voids filled with the dead bodies of anaerobic bacteria. The water can no longer soak away below the pipe so it rises up above the pipe.

This process starts from day one. Over several years nothing appears amiss, not until the water can only get away at a level above the pipe. And as it is so doing, blocks this breed of soil. This can go on for many years… slowly blocking the soil above, below and around the soakaway. A lot depends on the nature of the soil, the water regime and time and the number of people using the system.


The Septic Tank Has Three Zones

The bottom is for storage of the sinking solids, the top will form a crust often, but not always. This is the FOG i.e. fats oils and grease.

The volume of water below the floating grease and above the solids at the bottom is the Settlement Zone. Here the mixture of water, organic solids and chemically laden water is allowed to settle. A family of four would use 600 litres each day. The volume of the tank after being emptied, is 2800 litres for the smallest septic tank.

So the water has four or five days to move slowly through the tank, allowing solids in suspension to settle out. This volume is reduced after a year or so, now the water is taking just three days to pass through. lf the septic tank is not emptied, then the bottom solids increase in depth and the settlement zone is reduced… and so the speed increases.

If it is halved, then the speed is doubled and not all the solids settle out and so rather than 200 ppm going into the ground more like 230 to 250 ppm goes through, hastening the demise of the soakaway.

Now the water rises higher and higher above the perforated pipe. Till in fact it is above the tee pipes in a brick septic tank or FOG controlling baffles in a modern GRP tank. Now we have the grease escaping, accelerating the breakdown of the soakaway.

So many think it is because of heavy rainfall that winter. This obviously saturates the ground and makes matters worse but regularly de-sludging will help the life of the soakaway whatever the rainfall.


Manhole Cover Allerton Sewage Treatment

Eventually the water level in the solid affects not just the septic tank but the water in the manholes, so much so that you worry when you flush the lavatory or the kitchen waste pipe floods onto the footpath… Your investigations show the manholes to be full. Using less water helps but eventually you have to have the tank emptied more and more frequently.

This is where Allerton gets called in to solve the problem.  Installing a pipe into a ditch is not the answer as the Binding Rules make clear.

If there is a ditch, by treating the water so that the final effluent is not 200 ppm but 20 ppm then there is a very good chance that a permit from the Environment Agency can be obtained.

But what if there is no ditch? What if the soakaway area is limited to a small garden. What if access to the garden is by a metre wide gate preventing easy digging and movement of gravel and spoil to the tip??


What then?

Then Allerton will survey the situation, taking measurements, asking details questions and come up with an answer. The result is often the installing of the ConSept.

Allerton Septic tank conversion It is a piece of kit, made to measure, installed in the septic tank via the lid. The anaerobic bacteria are blown away by the powerful air blower which creates an aerobic condition and encourages the good aerobic bacteria to live, breed and multiply, living on the organic material and breaking down much of the chemicals too.



This is good news, sure, but how to get rid of the effluent when the soakaway has failed?

Allerton simply dig down to the outlet pipe and put an expanding plug in the pipe as it leaves the tank, preventing any water in the ground getting back into the septic tank.

Now the clever bit, we use the air syphonically to lift the treated water from the tank up to ground level, into a sample chamber just 200 mm deep.

Now we connect this chamber back to the existing soakaway pipe.

What happens next is that we now have cleaned water, akin to rain water, travelling along the perforated pipe, rising up above the pipe till it can move freely just below the topsoil. Once away from the contaminated soil, it finds its way down into the ground. The big difference is that the water is not backing up into the septic tank or any of the manholes between it and the house.

Eventually the clean water will have cleaned the contaminated soil and so the ground slowly has a chance to recover.


Sometimes this ideal doesn't work! What to do then?

The sample chamber is only 200 mmm deep and an additional pipe can easily be dug by hand at a very shallow depth, in the topsoil.  So a digger is not needed, just a Saturday afternoon of hard labour!

Think about this: Five people use 150 litres each so each day produce 750 litres. A roof 6 m by 10 m sheds its water to the down pipe and its soakaway, 60 sm x say 10 mm = 600 litres. Where does it go to?... Into the ground without you even knowing that there is a soakaway.

This is because it can soak away at a shallow depth and also because it is clean water, said to be about 5 ppm.

So our cleaned water is now almost on a par with roof water.

We have installed well over 1500 of the ConSepts, mainly putting the effluent back to the soakaway, but some of the tanks, with a permit from the EA, outfall into ditches.

We have twenty years of experience with these units and nearly 50 years’ experience in drainage of all kinds.

The units, like all we sell, need proper servicing and our British Water trained engineers are well qualified to do this.

Bempton Cliffs Sewage Treatment Diagram
(Jon said - 
has been replaced by a bloody big klargester
Serviced by a local firm. Dawson
We didn’t get a chance to quote.
I think!
Maybe we did. Either way I can’t write the blog. Actually I can if I keep it general. Or mention the name Rspb
Why can’t I?
Need to re-write so it's informative and truthful)
In the year of 2010 the RSPB contacted Allerton for advice on how to solve their sewage problem. They wanted install a very unusual septic tank.
  The purpose was to treat the effluent from the visitor centre which was attracting more and more visitors each year
The existing Septic tank had come to the end of its life, as septic tank systems do.
The pipe between the centre and the ST was long so installing a Sewage Treatment Plant was not an option due to noise and cost.
  The soakaway was not permitted to be parallel to the surface as it is with most systems, it had to soak into the limestone cliffs in consideration of nesting birds and their fledglings.
The plan was to install two concrete tanks and to then direct the water down two 250mm diameter bore holes approximately 6 metres deep
A steel sleeve was employed to ensure the effluent went into the limestone, rather than the top soil
Solids were collected in the bottom of the concrete chambers but the dirty water found its way into the rock by rising up in the tank and then entering the steel tubes a metre above the bottom of the tanks
The whole Job was carried out by Allerton at the optimum time of the year, that is when the birds had flown the nest!
This system lasted until the visitor numbers overwhelmed the design flow of the soakaway.
A Klargester Biodisc was then installed by Leo Dawson, a local Sewage Treatment company.

In 2011 the RSPB  at Bemton contacted Jon Allerton with a view to increasing the capacity of the septic tanks already there on the clifftop.
The Society planned to increase the size of the visitor centre and therefore needed greater capacity for the sewage treatment system.
They could not use a modern service treatment plant because any noise especially at nesting time might deter the birds from nesting.
The plan was to add to the existing septic tank system by installing a pair of deep boreholes 200mm diameter and 8m deep
Drillcorp were employed to bore the holes and Allerton constructed chambers using concrete rings.
A steel sleeve was fitted to prevent the treated effluent from infiltrating the clay layer in order to keep the surface free of pollution
The area was stripped of the topsoil and stored.
The risings or spoil, a mixture of chalk and clay, was spread over the area and the topsoil replaced
Within months, the site was as it was before and the new improved visitor centre was opened to visitors
An attenuation reservoir is a show pond created to take a fast runoff, store it and to let the water go into the watercourse at a much reduced rate!
On this occasion Jon Allerton was asked to provide a floating pump arrangement to remove water from a lake in Nottinghamshire after heavy rainfall. Cost was a major consideration and only a small amount of water would be permitted to enter a ditch which was, in effect, above the water level in the pond.
To do this, a frame was constructed to hold the pump so it was near the surface, not near the muddy bottom. The frame had to hold the pump and the floats. The problem was to get the frame and floats balanced so that it would keep the pump vertical, to save undue pressure on its internal bearings.
The arrangement, or raft, had also to bear the weight of the cable and the flexible 50mm pipeline, from the centre to the edge of the lake. Another float was added part way along the pipe line.
On shore, a control panel was needed to allow the pumping operation to be time controlled. This would allow a limited amount of water to be discharged and for it to be spread out over 24 hours. Several years later and our customer is well pleased.
Another job done!

Our History

23 Nov 2020
In 1966, Jon Allerton moved from his home in Buckinghamshire to Sleaford in Lincolnshire where he was a Ministry of Agiculture civil servant. His job was supervising the farmer's land drainage schemes.

Job Vacancy: Sales and Servicing Engineer

Are you looking for an interesting and rewarding career? Do you like the idea of working outside and seeing different parts of the country? Are you a people person with the ability to quickly build trusting relationships?

If so, Allerton have the ideal position for you. Due to expansion we are looking for an enthusiastic and hard-working individual to join our growing team.

Klargester Bearing and Disk Replacement

Job Role:

The successful candidate will form part of our servicing and sales team, travelling to sites across the U.K (sometimes staying away) to carry out the servicing of sewage treatment systems and pump stations. You will deal with break downs using problem solving and logical thinking to resolve the issue in a timely manner. 

Allerton engineer installing a manhole

Sales Element:

This role will also include an element of sales generation where you will be expected to engage with residential neighbours and surrounding businesses to those that you are visiting in order to create wider interest for our products and services. The successful candidate will have excellent communication skills with the ability to steer a conversation purposefully and not be afraid to ask for future business. 

What We Do:

The nature of the business is sewage and off mains drainage, so candidates must be comfortable with the idea of working in this industry.

Working alongside experienced members of the team, you will receive full training to carry out your role and become a valued and indispensable part of the field team.

As well as your usual maintenance role you will also be expected to assist other areas of the business, including our installation team where you could be involved in all aspects of installation work. Carrying out all site duties as required such as pipe laying, hand digging and reinstatement.

Allerton Gravel Wheelbarrow

About Allerton:

Allerton is a long established and successful company in the water treatment industry, specifically dealing with off mains drainage. Based in Sleaford, Lincolnshire, we supply, install and service a range of systems across much of the UK for both commercial and domestic clients. In Lincolnshire we have the dominant position, based on an outstanding reputation.

This is a full time, permanent position on completion of a probationary period. Basic hours will be 37.5 per week, working Monday-Friday with paid overtime required by the company for completion of works to deadlines. In the future there may be the opportunity for weekend work.

Role Progression:

Candidates should always be realistic about the opportunities for 'job title' advancement within any small company, but at Allerton we believe in trying to widen and develop skills by expanding the job role as much as possible. The successful applicant can be in no doubt that should they be ambitious, dynamic and a valuable member of the team, they will be rewarded with a widening of their roles and responsibilities. A candidate’s ability to take on extra responsibilities and the demonstration of additional skills will be a consideration during the interview process.

This is an excellent opportunity to join an interesting and unique business where you can have a big impact and become a valued member of the team.

Please apply by email only to: This email address is being protected from spambots. You need JavaScript enabled to view it.

Drilling hole for ConSept pipe installation