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Sewage treatment and Septic Tank Soakaway Advice

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Septic Tanks

If GRP constructed you can. If brick it will depend on sizes but if the depth of the water is below the inlet level more than 1.1m and volume of water is more than 2m then we can fit a ConSept.

Every 12 months, with a ConSept. Two years is possible, depending on the size of the Septic Tank.

No. All septic tanks should be emptied to protect the soakaway! Read the section about septic tank emptying.

NO, heavy rain can wash all the stored solids into the Soakaway or ditch or block the ConSept.

1. You will need to establish what type of water is flowing through each manhole on the property.

2. You will need to work out where the water from the stormwater manholes flows to e.g. into a ditch or soakaway.

Lift the manhole covers and observe. Have someone flush the toilets, then run the taps for the shower, then bath, etc. The water coming from each of these sources is foul water. And if you see it flowing through the manhole, it is called a foul manhole.

Once you establish that it is a foul manhole, then check to see that no stormwater goes into any foul manhole. To check that, on a rainy day stand in the rain with nobody in the house and see if any water goes through each foul manhole. On a summers day you can squirt water into the gutter to immitate rainfall. 

Afterwards, draw a plan of the property and show the foul manholes and pipes in red and the pipes and manholes for the stormwater in blue. This is also useful when you sell the house.

Yes. All lavatory, showers, wash basins, sinks etc are classed as foul. These must go to the septic tank. Rain water must NOT go into the septic tank.

The best ones are made from GRP, glass reinforced plastic. Or Polyetheylene. Concrete ring septic tanks are good but need two chambers.

Polyethene and GRP septic tanks should last 20 years at least, providing they are emptied every year to protect the soakaway and the baffle.

A sewage treatment plant, a cesspool, or a reed bed. If there is no room for a soakaway then a cesspool is used. These are huge tanks and expensive to install and expensive to have emptied.

The smallest septic tank is good for a four bedroomed house. Costs £600 to £750 plus vat.

It is proportionate to the number of people in the house, so it doesn’t matter. However, a septic tank for just laundry is not a good fit. It needs anaerobic bacteria to break down the organic waste and to help break up the chemicals in washing products. Speak to Allerton for advice on this before installing!

It’s difficult to gauge, so have it emptied every year. This will help lengthen the life of a soakaway. Read more about soakaways.

Carefully feel to see where the heavier sludge is. Deduct this from the depth of the tank and when there is a foot of sludge it is full. Any deeper and the settlement zone above the sludge level is compromised and the flow of water increases, carrying fine solids into the soakway. Not good.

Only if used excessively.

Septic tanks are not meant to be driven over. However, if a reinforced raft is constructed and there is a small gap between the surface concrete and the tank, then it should be fine. Take professional advice.

A septic tank costs about £2500 to replace but it is likely that it is the soakawy is what needs replacing. This can cost £2000. Ring Allerton.

You ruin the soakaway.

Just as good but often easier to install. A lot depends on ground conditions. 

It should emptied regularly by a registered waste contractor. The mess inside the walls of the septic tank is actually full of bacteria and should be left alone. Do not hose it down!

Every year as a rule.

Perhaps every two years if only two or three people are using it.

Yes if the house is right in other regards. But, have it surveyed first. That is most essential.

All waste water does not have to go to a septic tank. It could go to a cesspool, a sewage treatment plant, or a septic tank… or better still to the mains. 95% of sewage in the UK goes to the mains. 

Yes, every year to protect the soakaway.

The term BioDisc refers to a Sewage Treatment Plant made by Klargester. It is not a septic tank.

It can be discharged to the ditch without EA permission as it is an Exempt unit. It can also discharge to a soakaway if there is no ditch. Read the section about a Klargester repair on this post Engineers at Work for more information.

YES, if there is room.

ConSepts

 A conversion of a septic tank, a cesspool, a well, or some other underground tank to a sewage treatment plant.

YES, but only if you obtain a permit from the EA. Though Allerton will help you with it. Contact us for more details.

NO. But you do if you decide to outfall it into a ditch.

Check pumps, insitu, takeout, strip and clean, check distributor head/wiring junction box/panel and timer if applicable.

Too much back pressure for the air blower. Needs desludging. Discuss this with the Service engineer.

Immediately, and you can use both shower and washing machine later in the day.

Although wet wipes won’t block the ConSept itself, they can block drains and soakaways, or cause pollution if discharged into a ditch, so general advice is to never flush them.

Turn it off and on again.

ConSept in a GRP septic tank, once every 2 years but in a brick tank better to empty every year. Discuss with the Service Engineer. He is in a better place to make judgement.

Bleach can be used in moderate amounts. The unit should not smell like a ST and bleach in excess is not needed. A cap full per week should be enough, preferably not all on one day.

Yes.

Soakaways

YES, if there is room.

Soakaways from Septic tanks are bound to get blocked. Raw sewage has 300 parts per million (ppm). Water from a septic tank is not much better at 200 ppm. So those fine particles start to block the soakaway and the ground below and around the soakaway pipes from day one!

It is very hard to maintain a soakaway. Like all filters, they block!

The more permeable the soil, the longer the soakaway lasts. It is important to not let the floating solids escape into the soakaway by having the septic tank emptied annually.

The water in the outlet pipe is covering the bottom of the pipe. It should be free of water!

Soakaways have a limited life, even if the septic tank is emptied annually. It is a filter in effect. All filters get blocked eventually.

The soakaway is as deep as the outlet pipe as it leaves the septic tank. If it is in the ground too deep it may not work at all! Clay at depth is much more like plasticene and clay is used to line reservoirs and canals! If sandy, the soakaway will work much better, but not if the table rises in a wet winter to a level near the soakaway pipe. A wet flannel is useless! Read more about soakaway sizing in on our percolation test page. 

The ground is full of earthworms and other worms. They don’t like anaerobic conditions.

I do not think that they work and so I would not use them!

Not as a rule. They are limited in their life. Sometimes if they’re too deep they have a very short life!

Generally 5-25 years.

The best soakaway for sewage effluent is gravel. The Environmental Agency and British Water say the plastic soakaway bales should only be used for stormwater, i.e. water that is not foul.

  • The way to install a foul soakaway is to lay perforated pipe 100 mm diameter as flat as you can. This prevents all the water rushing to the far end, having missed the clean gravel in the first part!
  • The gravel should be single size, so as to have the biggest voids.
  • The bed should be 600 mm wide and about 300 deep. 
  • For septic tank water, you will need to replace the soakaway in another part of the garden some 5 to 25 years later. NO one knows!

7 metres or more.

Rainwater drain pipes and gutters should be checked in December and cleared of grit from the roof, bird droppings, dirty leaves, any grass and sycamore seeds in particular.

At the foot of the down pipe, the back inlet gulley and its grid should be cleared of all debris. This does mean plunging your hand into the gulley to remove all the leaves, etc.

Any accumulation means that future solids will overflow into the storm soakaway, reducing its life. Rainwater soakaways tend to be shallow and rainwater has about 5 ppm solids to water. Septic tank water is 200 ppm or more!

See BS6297 2007: Code of Practice for the design and installation of drainage. Fields for use in Wastewater Treatment.

I’m afraid it does. Septic tanks seldom fail!

Victorian septic tanks were designed for far less water usage than today’s profligate use. But it is generally the soakaway that needs replacing. This will need to go in another part of the garden if the existing ones position is known and if there is space. The garden may have many old systems. No one knows!

Both terms are used for the same thing. A system of pipes used to disperse water underground!

It is not good to dig a hole and fill it with stones, bricks, or other hard material. It’s far better to have a long pipe with clean, single size gravel under the pipe. This way the load is spread over a large area, not all in one place.

Many houses have soakaways for the downpipes from the roofs. Because rainwater is clean, the soakaway works faultlessly. That is providing the gutters are cleaned and the back inlet gulleys emptied.

All soakaways should be as shallow as possible.

  • If you are having to pump, keep the pipe to within 100 mm from the surface.
  • Water travels quickly in topsoil, both laterally and downwards.
  • Dig a hole 3 feet deep in clay soil and dig a hole 1 foot deep nearby.
  • Put a bucket of water in each hole and observe. 

Read more about septic tank soakaway sizing and length on our percolation test page.

The householder. The tenant or the landlord if it is in the agreement. The local council will not maintain drains on private land.

That depends on the nature of the water percolation test. Rainwater at 5 ppm? Treated effluent from a sewage unit at 20 ppm? Or effluent from a septic tank at 100 ppm?

Yes.

No! Rain can be so heavy and in large volumes of rainwater can flush away all the carefully settled solids in one go! All into the poor old soakaway, clogging it with yet more solids and worse, floating solids, i.e. fats and oils!

If the ground is bone dry then a lot of water is needed, maybe bucketsfull for each test hole. If there is water in the bottom of the hole as you dig it then the percolation test will be pointless. See BS6297 2007: Code of Practice for the Design and installation of Drainage. Fields for use in Water Treatment. Please read our Percolation Test blog post for more information.

A soakaway to take water from roofs and hard surfaces, yards and patios for example.

Probably. The roof water could be led to a ditch however. In some areas, like Lincoln, both roof water and foul water are taken away in the same pipes.

Farmers farm clay soils very profitably providing they are properly drained. The pipes are about 700 mm deep, are laid with a fall as little as 1 in 1000. They need gravel over the pipe in order to collect water from the surface. The farmer helps this process by deep cultivations such as mole ploughing and subsoiling.

Crates are very good for rainwater but not permitted for septic tank water or treated effluent from a sewage treatment plant. The number depends on the percolation test results and the roof area and the annual rainfall in that area.

Call for the desludger, rod the drains, stop using water where possible, panic and then ring Allerton!

Sewage Treatment

Converting horrible sewage into relatively clean water and using nature to do it seems like a miracle at times. To do it is not so easy though. That is the constant challenge.

Yes. For links and more information, check out our page on binding rules.

They are all good. They have to satisfy rigoruos testing with human sewage for a long period. Personally I prefer the WPL Diamond. 

If there is excessive use of chemicals, then the bacteria are killed. We need the aerobic bacteria to break down not just the organic matter, but the chemicals as well.

We use bleach and other agents for cleaning the house and chemicals on our hair and bodies. We use chemicals to sterilise our hands. We use all sorts of powerful agents in the kitchen sink. All this has to be neutralise by our friendly bacteria. If too much chemical is used, then they can’t do the job properly.
 
Oil and grease suffocate the aerobic bacteria, allowing the anaerobic bacteria to make the whole lot septic again. Putting spent oil into a bottle is better than down the sink.
 
So, everything is permitted but in moderation!

 

 All sewage systems work by adding oxygen to the sewage which passes through.

 These days it is mainly done by passing fine air bubbles through the water, allowing the bacteria air as well as food and water. They convert the sewage to harmless gases in the air. 

Not necessarily. It can quite easily go to a ditch or river or other running water.

Soakaways are fine though. Effluent from a septic tank has 200 ppm. Water from a sewage treatment plant has less than 20ppm.
Rainwater is quite clean and about 5 ppm. Tap water is zero of course

The Environment Agency and British Water reckon on a 4 bedroomed house being 6 PE (population equivelent).

This generally needs a plant about 2 metres in diameter by just less than 3 metres deep. Much bigger than a septic tank.

To simply install a sewage treatment plant it would cost between £3300 and £4000 in normal conditions

Rock makes it more expensive but running sand can double the cost. Try digging a hole on the beach where the tide has just gone out!

There is more information and a comparison table in the about septic tanks section of our septic tank soakaway problems page.

Allerton has units that we still service and they are 25 years old and going strong.

Klargester are even older!
 
They are not made for a limited life as white furniture is. They do need to be maintained though. Fortunately there are no moving parts in the WPL units. The diamond Sewage Treatment Plant relies on a blower and when we service the unit we make sure the blower is good for another year at least. We are constantly refurbishing and replacing them so as to keep them working consistently. I cannot think of anything else that lasts as long. 

 Read our Klargester Biodisc blog post for more information about BioDiscs

 This is a piece of kit which converts raw sewage to clean water. Not clean enough to drink of course as it can still carry E. coli and other pathogens.

It is high in nitrates and phosphate. I should not be sprayed onto plants but can be used as underground irrigation. Roots have the ability to take what they want and to leave the pathogens in the ground.

People over the centuries have tried very hard to make an effective sewage treatment Plant. You need chemists and engineers working together to get the right balance of air, water volumes and flows. 

A sewage treatment plant coverts foul water into clean water, not perfect but good enough to go into rivers and streams.

To size a sewage treatment plant go to our Diamond Sewage Treatment Plant page.

The blower makes a noise and bubbling makes a noise. How noisy depends on your hearing and expectations.

 If you are going to sit in the garden near one it would be good to vist someone with the same model. The biodisc is relatively quiet.

Dozens. Plenty to choose from, but best get to see one and see the quality of effluent coming form the unit. Ask questions. Contact us for more information.

Never. Treated water does go into rivers. The Trent and Thames for example. But while water is abstracted from the rivers and reservoirs, it is chemically treated before we drink it.

Sewage is waste water from the lavatory, kitchen sink, wash basins, baths, showers and washing machines.

The first thing is to settle out all the solids, organic and inorganic. The dirty water then is treated with air. Just air. The aerobic bacteria need oxygen and food so they feed on the organic matter, converting it to gases we find naturally in the air.

Wastewater poisons the ditches streams and rivers.  So little can survive in it.

Sludge is the solids that collect in a septic tank or sewage treatment plant and it needs to be removed to be dealt with by the Water Authorities.

A properly service sewage treatment plant smells a little. It reminds me of the smell walking in a wood, scuffling your feet through the leaves.

Genarally no, but if the sewage gases get too strong then it can kill. We use confined spaces staff and certified equipment when we go into a sewage treatment plant or st or ps.

Get it serviced properly. Check that it is not being overloaded above what it was designed for. Prevent grease getting into the system by checking the grease trap. Check that rainwater is not getting into the system

None.

All that you bring into the house. Without the lavatory waste, the plant would stuggle to break down all those chemicals that we buy in bottles!

 Generally sewage from a house can be called waste water or sewage wastewater. Commercial waste water covers a whole lot of chemical processes. Food production, factory waste, abattoirs, irrigation, and swimming pool water.

The humble sewage treatment plant can not deal with this and special treatment systems are employed.

By encouraging aerobic bacteria to digest the organic matter.

 

All sewage is dangerous and needs to be dealt with carefully, by people properly trained by British Water.

Yes as it has nitrogen and phoshates in solution.

This depends on the loadings.  Packaged sewage treatment plant come in sizes such as 6pe, 10 pe, and so on. 

We call it “treated effluent” It looks clean but it still carries chemicals and pathogens. 

The rivers would become polluted and poisonous, not just to fish and plants, but it could cause pandemics that would wipe us all out!

Raw sewage is all the waste from the house. Lavatories, baths, showers, wash basins, kitchen sinks, washing machines, dishwashers, etc.

Klargester was probably the first company to sell packed Sewage Treatment Plant in large numbers.

 I guess the price then was similar to today’s prices but allowing for inflation, very much cheaper today than then. And much improved too. 
 
Find more information about Klargester in the Klargester repair section in this blog post: a Day in the Life of a Service Engineer 

For Diamond units, every 3 to 5 years.

Laws and Regulations

Read the General Binding Rules or ring us. Also see the official general binding rules.

YES