Drainage

Count how many things are affected. One fitting misbehaving on its own — just the basin, just one toilet — points to a blockage close to that fitting. Two or more at once, or a toilet that bubbles when you empty the bath, points to the shared pipework they all drain into.

The check that settles it is the manhole. Lift the cover nearest the house and look. If the chamber is full or the water is standing still, the blockage is somewhere downstream of that chamber. If it is empty and dry, whatever is wrong is between the house and that point, so it is inside your pipework.

A manhole — an inspection chamber, properly — is an access point built into the run of a drain, usually where pipes join or change direction. It lets the drain be inspected and rodded without digging anything up. Most properties have one fairly close to the house and another near the boundary, under a square or round metal or plastic cover in a path, driveway or garden.

It depends where the blockage is. You are responsible for the pipes inside your boundary that serve only your property. The sewer beyond your boundary, and pipes shared with neighbouring properties, belong to your water company — that has been the case since the private sewer transfer in October 2011, whatever condition the pipes were in.

Thames Water, who cover most of London, describe the split by symptom: if the problem is outside your boundary, or more than one property is affected, it is one for them. If only your home is affected and there is no other flooding locally, the blockage is very likely on your own drainage. Reporting it to them first costs nothing and is worth doing when the signs point outside your boundary.

Ring us rather than booking online if it will not wait — the phone gets you straight to someone who can tell you when an engineer can reach you.

It depends where it is and what it is made of. Close to a fitting, a plunger, a hand auger or taking the trap off is usually enough. Further along, drain rods pushed in from an access point will shift most things.

For anything solid or stubborn there is high-pressure water jetting, which is a hose fed down the drain that cuts the blockage apart and scours the pipe wall as it goes. Roots and hardened scale need electro-mechanical cutting instead — a rotating flexible cable with cutting heads on the end. If the same blockage keeps returning, a camera down the drain shows whether something structural is causing it.

We would not. Caustic products can struggle with the blockage and still sit in the pipe, and standing chemical is a hazard for whoever opens the drain next — including our engineer. If you have already used some, just tell us when you call so they arrive knowing.

A blockage that returns is usually a symptom rather than the problem. Fat and grease build up on the pipe wall until the bore is too narrow for normal use. Roots find a cracked joint and keep growing back. A section of pipe has sagged, cracked or partly collapsed, so waste no longer runs away cleanly. Clearing it fixes today; a camera survey shows which of those is behind it.

Indoors, mostly fat, oil and grease poured down the sink, which cools and sets on the pipe wall and then catches everything else. Wet wipes are the other big one — including the ones sold as flushable, which do not break down like paper does. Outdoors, it tends to be tree roots, silt and leaves washed into gullies, and the odd broken pipe.

Stop running water anywhere in the house — no taps, no toilets, no washing machine — because everything you send down has nowhere to go but back up. Keep people and pets away from it. Then call us. If you can safely lift the manhole cover and tell us what is in there, that helps the engineer arrive prepared.

Yes. Gullies, manholes, inspection chambers and the underground runs between them, as long as they are within your boundary and serve your property. Where a blockage turns out to be in the shared sewer beyond that, we will tell you, because that one belongs to your water company rather than to you.