CLEARMASTERS
The problem
Why what you flush matters
Every week our tankers and jetting crews clear drains, pumps and tanks blocked by things that should have gone in the bin. It isn’t just our customers: it’s a problem right across the UK’s sewers.
Figures from Water UK’s fats and wipes campaign.
On mains drainage
Your pipes run to a public sewer. A blockage in the pipes that serve only your home is your responsibility to clear, and a blockage further down can flood your garden, your neighbours or the street.
Fat and wipes that get past your drains end up in fatbergs, the huge masses of grease and wipes water companies dig out of sewers.
Off mains
If you have a septic tank, a treatment plant, a cesspit or a pump station, the problem stays on your property. You pay for the extra emptying, the call-outs and the repairs.
These systems are much smaller than a public sewer, so it takes far less to cause trouble.
The golden rule
Only flush the 3 Ps
It’s the rule every water company in the country uses, and it applies to every kind of drainage system.
Pee
Urine is mostly water.
Poo
What the system is built for.
Paper
Toilet paper only, in sensible amounts.
Everything else goes in the bin
Wipes, cotton buds, sanitary products, nappies, floss, kitchen roll and tissues. Keep a small bin with a lid in every bathroom: it’s the simplest fix there is.
What about “flushable” wipes? Wipes labelled flushable still don’t break up the way toilet paper does. The water industry’s own Fine to Flush certification ended in 2024, and water companies now ask everyone to bin every wipe.
The plastic wipes ban. From 19 May 2027, shops in England can no longer sell wet wipes that contain plastic, with similar bans coming in Wales, Scotland and Northern Ireland. That’s good news for rivers and beaches, but plastic-free wipes can still block a pipe or jam a pump, so they still belong in the bin.
Test yourself
Flush it, bin it, or take it elsewhere?
Sixteen everyday items. Pick where each one should go and see how you score. Some of the answers surprise people.
Inside the pipe
How a blockage forms
Blockages rarely happen in one go. They build up over weeks or months, which is why a drain that “was fine yesterday” can suddenly back up. Step through it below.
Fat, oil and grease leave the kitchen as a warm liquid, so they seem harmless going down the plughole. A squirt of washing-up liquid makes no difference: it only carries the fat a little further.
Underground pipes are cold. The fat cools, turns solid and sticks to the pipe walls, building up layer by layer and narrowing the pipe.
Wipes, cotton buds and hair catch on the sticky fat, on rough joints and on tree roots. Each one catches the next, and the flow slows down.
Eventually the pipe closes completely. Sewage has nowhere to go, so it backs up into the lowest point: usually a manhole, a downstairs toilet or a gully outside.
Already blocked? Our drain unblocking crews clear fat and wipes with high-pressure jetting, and a CCTV survey shows what’s really going on.
In the kitchen
Fats, oils and grease
Fats, oils and grease, often shortened to FOG, are the single biggest cause of blocked kitchen drains. It isn’t just the pan of bacon fat: butter, gravy, sauces, salad dressings, mayonnaise, milk and cream all carry fat down the sink.
Hot water doesn’t help. It keeps fat liquid just long enough to get it out of sight, then it sets further down the pipe, often under the drive or the garden, where it’s harder to reach.
On a septic tank or treatment plant, fat forms a thick crust on top of the tank and can pass out to the drainage field, where it seals the soil and stops water soaking away.
Do
- Let fat and oil cool, pour into a jar or bottle and bin it
- Wipe greasy pans and plates with kitchen roll first
- Scrape food into the bin or your food waste caddy
- Use a sink strainer and empty it into the bin
- Take large amounts of oil to the recycling centre
Don’t
- Pour fat down the sink, even with hot water
- Rely on washing-up liquid to “break it up”
- Rinse plates of gravy, sauce or curry straight into the sink
- Put fat down an outside drain or gully
What you pour
Chemical overload
Normal cleaning is fine on any drainage system. The trouble starts with heavy, regular use, or with chemicals that should never go down a drain at all.
Use sparingly
Bleach, disinfectant and antibacterial sprays. Fine in normal amounts. On a septic tank or treatment plant, daily heavy use kills the bacteria that treat the sewage.
Laundry and dishwasher detergent. Spread washing across the week rather than doing it all on one day, and don’t overdose.
Water softener regeneration water. If you’re off mains, check your softener and plant manuals: some manufacturers advise keeping the salty regeneration water out of a treatment plant.
Never down any drain
Paint, white spirit, thinners and solvents. Water treatment can’t remove them, and they wipe out the bacteria in an off-mains system.
Engine oil, antifreeze and fuel. Take them to a recycling centre that accepts them.
Weedkillers, pesticides and pool chemicals. Chlorinated pool or hot tub water also kills treatment plant bacteria in one go.
Medicines. Take unused tablets and liquids back to a pharmacy.
Caustic drain unblockers rarely shift a proper blockage. They can damage older pipes and, on a septic tank or treatment plant, they kill the bacteria too. If a plunger won’t clear it, it’s time for a jetting crew rather than another bottle.
Outside drains are different. Many gullies and road drains are surface water drains that run straight to a stream or ditch with no treatment at all. Never tip paint, oil, cleaning water or anything else into them.
Pump stations
If you have a pump station
A pump station collects sewage in an underground chamber and pumps it uphill to a sewer, septic tank or treatment plant. It’s the least forgiving system of all for the wrong things going down the loo. Tap the numbers on the diagram.
Wipes and rags wrap round the pumps
Pumps in a domestic or small commercial station are small. Wipes, sanitary items and floss wind round the impeller until it jams. The pump strains, overheats and trips out, or burns out altogether.
Fat floats and coats the floats
Fat and oil rise to the top and form a crust. It coats the float switches that tell the pumps when to start and stop, so they stick. The pumps don’t start, the level rises and the high-level alarm goes off.
Debris jams the non-return valves
Each pump pushes sewage up through a one-way valve. A wipe or a lump of fat caught in it lets sewage drain back into the chamber, so the pump runs over and over again and wears out early.
Everything ends up in the rising main
Sewage is pushed uphill through a narrow pressure pipe. Fat sets on its walls and narrows it year by year, so the pumps work harder for less flow.
The alarm is your early warning
If the alarm sounds, cut your water use straight away and call us. Our guide to why a pump station alarm sounds explains what each warning usually means.
Pump stations that serve several homes, holiday lets, offices or care homes are worst hit, because you can’t control what everyone flushes. A sign in each toilet and a bin in every cubicle really do help.
Regular pump station servicing catches rags and fat before they stop the pumps, and a periodic pump station empty clears the crust and sludge that build up in the chamber. If a pump has already failed, see our pump station repairs page.
Off mains
Septic tanks and treatment plants
A sewage treatment plant is a small sewage works in your garden. It relies on living bacteria to clean the waste before it’s released, so what goes down your drains decides how well it works. Tap the numbers to explore.
The primary tank fills with things that never break down
Solids settle here first. Wipes, sanitary items and cotton buds can’t be digested, so they build up, fill the tank faster and block the pipes and air-lift pumps that move sewage between chambers.
Fat forms a crust and coats the media
Fat floats to the top as a thick crust. If it carries over into the biozone, it coats the media the bacteria live on and cuts off their oxygen.
Chemicals kill the bacteria doing the work
The biozone is full of living bacteria that break sewage down. Heavy use of bleach, disinfectant, antibacterial sprays, drain unblockers or solvents kills them. Treatment slows, the plant starts to smell and dirty water leaves the outlet.
Too much water at once washes it through
Five loads of washing on one day, emptying a hot tub or rainwater connected to the plant can push sewage through before it’s treated. Spread laundry across the week and keep rainwater out.
Poor effluent damages what’s downstream
Whatever the plant doesn’t treat goes to your drainage field, soakaway or ditch. Solids and fat clog a drainage field, and polluted discharge can break the Environment Agency’s general binding rules, which you’re responsible for.
Septic tanks
A septic tank doesn’t have a biozone, but it still relies on bacteria to break down solids before the liquid flows to the drainage field. Fat, wipes and chemicals cause the same problems: the tank fills faster, the crust thickens and solids carry over into the field.
A drainage field clogged with fat and solids stops draining, and once it’s failed it usually has to be replaced. That’s far more expensive than a bin in the bathroom.
Keep it healthy
Leave your treatment plant switched on, even when you’re away: the bacteria need air to survive. Keep rainwater and pool water out, avoid food waste disposal units unless your plant is designed for them, and tell us at the service if anyone in the house is on a long course of strong medication.
Most important of all, get it desludged and serviced on time. You don’t need to add septic tank treatments: a healthy system gets all the bacteria it needs from everyday use.
Early warning
Signs something’s building up
Most drainage problems give you warning before they become an emergency. Catching them early usually means a quick jet or an empty rather than an overflow and a repair bill.
If any of these sound familiar, give us a call on 03333 233566, or book online. If sewage is already escaping or an alarm won’t clear, see our 24/7 emergency page.
What goes where: the cheat sheet
Flush
- Pee
- Poo
- Toilet paper
That’s it. Nothing else.
Bin, don’t flush
- Wet wipes, even “flushable”
- Kitchen roll and tissues
- Cotton buds, cotton wool
- Sanitary pads, tampons, applicators
- Nappies
- Condoms
- Dental floss
- Contact lenses
- Plasters and bandages
- Hair
- Cat litter
- Cigarette ends
- Cooled fat and oil, in a container
Not down the sink
- Fat, oil and grease
- Food scraps, sauces, gravy
- Coffee grounds and tea leaves
- Rice, pasta and bread
- Large amounts of bleach or disinfectant
- Caustic drain unblockers (septic tanks and plants)
Take it elsewhere
- Medicines: pharmacy
- Paint and white spirit: recycling centre
- Engine oil: recycling centre
- Garden chemicals: recycling centre
- Large amounts of cooking oil: recycling centre
- Food waste: your food caddy
Clearmasters · Septic tanks, treatment plants, pump stations and drains · 24/7: 03333 233577 · clearmasters.co.uk
Questions answered
Flushing and drains FAQs
Are flushable wipes safe to flush?
No. Wipes sold as flushable don’t break up quickly enough in pipes and sewers. The water industry’s Fine to Flush certification ended in 2024, and water companies now ask everyone to bin all wet wipes. On a septic tank, treatment plant or pump station they cause problems even faster.
Will the plastic wet wipes ban stop blockages?
It will help. From 19 May 2027 shops in England can no longer sell wet wipes that contain plastic, with similar bans planned in Wales, Scotland and Northern Ireland. Plastic-free wipes still don’t break down like toilet paper, though, so they should still go in the bin.
Is it OK to pour cooking oil down the sink with hot water and washing-up liquid?
No. Hot water and washing-up liquid only carry the fat further down the pipe, where it cools and sets. Let oil and fat cool, pour them into a container and put them in the bin, and wipe greasy pans with kitchen roll before washing them.
Can I use bleach if I have a septic tank or treatment plant?
Yes, in normal household amounts. It’s heavy, regular use of bleach, disinfectant and antibacterial products that kills the bacteria your system relies on. Use them sparingly, avoid pouring them in neat and spread big laundry days across the week.
Do I need to add septic tank treatments or enzymes?
Most systems don’t need them. A healthy septic tank or treatment plant gets all the bacteria it needs from normal everyday use. If yours smells or keeps struggling, it usually points to a different problem, such as overdue emptying, a fault or chemical overload, so it’s worth having it checked.
Can I have a food waste disposal unit with a treatment plant?
Only if the plant was designed for the extra load. Ground-up food adds a lot of solids and fat, which fills the tank faster and can overwhelm the bacteria. Check with the plant manufacturer or ask us before fitting one.
Should I switch my treatment plant off when I go on holiday?
No. Leave it running. The bacteria need air from the blower to survive, and switching it off can kill them and damage moving parts. The plant will cope with a quiet spell while you’re away.
What should I do with old medicines?
Take them back to a pharmacy, which will dispose of them safely. Don’t flush them or pour them down the sink.
Got a different question? Call 03333 233566 or send us a message.