The short answer
Yes, ordinary toilet paper is safe for septic tanks. It is designed to break apart in water, and the tank's bacteria deal with what is left. Thinner papers break down fastest, while very thick quilted ones take longer. Wet wipes, kitchen roll and tissues are the problem, because they don't break down and they cause most blocked outlets.
There is no need to buy special septic tank paper, although some brands market it that way.
Which toilet paper breaks down best?
Single and standard two-ply papers break up quickly. Recycled toilet paper usually does too. Thick three or four-ply quilted papers hold together longer, which in a well-run tank is rarely a problem, but in a small or overloaded tank adds to the sludge.
Paper that breaks down slowly is more of an issue for the pipework than for the tank. Long, flat drain runs with little fall can catch it, especially if other things are holding it back.
A simple test
Put a few sheets of your usual paper in a clear jar with water, close the lid and shake it for 15 seconds or so. If the paper breaks into small pieces, it will be fine. If it stays in large clumps, consider a thinner brand, particularly if you have had blockages before.
What should never be flushed
- Wet wipes of any kind, including those labelled flushable, unless they carry the Water UK Fine to Flush mark.
- Kitchen roll and paper towels, which are made to stay strong when wet.
- Facial tissues, for the same reason.
- Sanitary towels, tampons and their applicators.
- Nappies, cotton buds, cotton wool, dental floss and contact lenses.
- Cat litter, even types sold as flushable.
On a septic system these items end up in the tank, where they build up in the scum layer, block the outlet and dip pipes, and can reach the drainage field. On a treatment plant they also foul pumps and float switches.
How much toilet paper is too much?
Normal household use is fine. Large wads flushed at once can block the toilet trap or the pipe before they reach the tank, so if someone in the house uses a lot, flushing more often helps. The tank itself copes with normal amounts and it all comes out at the yearly emptying.
Do you need additives to break paper down?
No. A septic tank does not need enzymes or bacteria from a packet to deal with toilet paper. The bacteria that arrive with every flush do the job, and the yearly emptying removes what has built up. Our page on whether septic tank tablets work goes into the evidence.
Signs of a paper-related blockage
A single toilet that drains slowly usually points to a blockage in its trap or branch pipe. Every fitting draining slowly points further down, to the main drain, the tank or the drainage field. Our guide to toilet flushing problems covers the cistern side.
If blockages keep happening, an inspection can look at the tank inlet, outlet and dip pipes. Our septic tank inspections find where things are catching, and our repairs team clears and fixes them. For the rest of the everyday habits, see our maintenance dos and don'ts.
