How do I stop drains blocking?

Fat, hair and wipes cause almost every blockage — the habits and the ten-minute monthly job that prevent them.

Difficulty: beginner
Time: 30 min
Read: 2 min
Safety: caution

Short answer

Never pour fat down the sink and never flush wipes, even ones labelled flushable. Those two rules prevent the large majority of household blockages, and a hair catcher in the shower prevents most of the rest.

Blockages are almost entirely preventable, and the prevention is much cheaper than the cure. Three materials cause nearly all of them, and each has an easy alternative.

Safety

Never mix drain cleaning products — combining different chemicals can produce toxic gas. Caustic drain cleaners burn skin and eyes; wear gloves and goggles and never use them with a plunger, which can splash them back. Do not use caustic products in a toilet or on a completely blocked drain where they will sit.

Step by step

Never pour fat or oil down the sink.It solidifies as it cools and coats the pipe, catching everything else. Pour it into a container, let it set, and put it in the bin.
Wipe greasy pans before washing.Kitchen paper into the bin first. It removes most of the fat before any water is involved.
Fit a hair catcher in the shower and bath.A few pounds and it prevents the single most common bathroom blockage entirely. Empty it weekly.
Never flush wipes, cotton buds or sanitary products.Wipes do not break down, whatever the packet says. They are the main component of most serious sewer blockages.
Use a sink strainer in the kitchen.Food scraps, tea leaves and coffee grounds all accumulate. Coffee grounds in particular compact into a solid plug.
Flush drains with hot water weekly.A kettle of hot water down the kitchen sink once a week helps move fat along before it sets. Not boiling if you have plastic pipes or a ceramic sink.
Clean out the gully and the grate outside.Leaves and silt collect in outside drains, particularly in autumn. Five minutes with a gloved hand and a trowel.
Deal with slow drainage immediately.Slow is a partial blockage. It is easy to clear at that stage with a plunger or a drain snake, and expensive once it becomes complete.

Tips

A handful of bicarbonate of soda followed by vinegar, then hot water, is a reasonable monthly maintenance flush. It is not strong enough for an actual blockage.
A drain snake costs very little and clears hair blockages that no chemical will shift.
If several fixtures back up at once, the blockage is in the main drain rather than one pipe. That usually needs professional attention.

Common mistakes

Flushing wipes labelled flushable — They do not disintegrate like paper. They are the primary cause of large sewer blockages and of many household ones.
Mixing drain cleaning chemicals — Different products can react and produce toxic gas. Never combine them, and flush thoroughly between different treatments.

Questions people ask

What causes most drain blockages?

Fat in kitchen drains, hair in bathrooms, and wipes in toilets. All three are entirely preventable with habits rather than products.

Are flushable wipes really flushable?

They pass through the toilet but do not break down in the sewer. They are a major component of blockages and should go in the bin.