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Blocked Drain - Unblocking a tenants drain

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Possibly the most frequent maintenance call-out we get from tenants is for blocked drains. Tenants usually phone up saying 'The water won't go down the sink!' Most often it's the kitchen sink that is blocked and it's usually because the tenant has put food down the plughole. Your investigation may reveal a load of rice or pasta down there, but the tenant will invariably be mystified as to how it got there.

DIY Basics - for more DIY information

The first thing you can do if the water's not moving at all and the sink's half-full of water, is to use a plunger. Not the traditional rubber hemispherical type - a better version of plunger is a plastic concertina or even a sort of big syringe: these produce a far greater range of pressures, which can blast through the blockage.

If that fails, you can start dismantling the pipes to clean each section. You can also buy a flexible rod of about 30 feet long that you can poke down pipes, which may either be like a thin metal ribbon or may be coiled. This will sometimes clear the blockage. Some types can be passed through plugholes but I prefer to use them only beyond the dismantled U-bend, as there is a risk they could get stuck.

If that doesn't work you can try using something like 'Dambuster'. It's quite expensive at £20 a bottle, so avoid using it whenever possible. Don't get it on your skin, because it's very caustic and will cause burning! You can pour Dambuster down the plughole, or down the open end of a dismantled pipe (to avoid it sitting in the U-bend). It dissolves oil and fat, grease, hair and paper (even cigarette ends). It makes a wonderful burning smell and the plastic pipes get hot due to the acidic reaction. Milder drain-unblocking products may not worth using in situations where there is a serious blockage problem.

With a bath it's more difficult to dismantle the pipes because of restricted access so the Dambuster, plunger and flexible pipe passed through the plughole may be the only options."

Contrary to what the layman may think, a 'U-bend' does not refer to the third person singular verb conjugation, or your position when you're trying to find it, it does in fact refer to the pipe bend that looks like a 'U' under the sink. It's full of water and the idea is that it stops smells from your drain coming up through your plughole. It's a sharp U shape so you can't poke anything through it - that's why you have to remove it if you want to poke anything beyond there. The U-bend may in fact be where your blockage is, so when you take it off you can have a look and see if that's full of muck.

Some sinks have something that's called a bottle trap, which is actually a three-inch diameter pipe that forms a U-shape, with a cap on the bottom. When you remove the cap, all the muck falls out. So you can have either a bottle trap bottle trap or a U-bend underneath the sink."

You take the U-bend pipe off by unscrewing the white plastic nuts that hold it on. They might be too tight to do by hand, so you may need a pair of water pump pliers with a jaw capacity of about 50 ml.

If the sink is only partially blocked, it may pay off to run the tap for a few minutes so when you do remove the U-bend, at least the water will be reasonably clean - remember to have a bucket handy underneath!

That's how to unblock the 40 mm plastic pipe that you find above ground, between the sink and the sewer. If the blockage is below ground, in the sewer, you will have to use drain rods. You can buy a set of drain rods for about £20 from a plumbers' merchant. They're a bit like the sort of thing a chimney sweep uses - they screw together, there's usually ten in a set and each piece is about three feet long, so you can make up a 30 foot flexible rod and shove that down the drain. It may be worth getting two sets so you can make up to double the length, as can sometimes be needed.

You will need to lift a manhole cover to access the drains. You could invest in a manhole cover key, but there's usually some sort of tool that you can use to improvise, to get hold of the manhole cover and lift it up. Manhole covers are very heavy (some of them are made of concrete) so don't drop them - especially on your toe.

To identify the correct manhole: you can usually tell which way the sewers run by the slope of the ground. If the ground slopes away at the back of the house for example, that will probably be where the sewers run - so any manhole cover in the back garden will give you access to the drain in question. If when you take the cover off you find the drains are full of mucky water that means the blockage is beyond that point. So you need to go to the next manhole cover along. What you're doing is looking for one that's empty and then you can put your rods down there in the direction of the one that's full, knowing that the blockage is somewhere between the empty and the full one. If you use the corkscrew type head on the drain rods, then you can usually get hold of the blockage and pull it through. It will all come whooshing through and will be cleared.

Strictly speaking, there is often a clause in the Assured Short hold Tenancy agreement to say that if the tenant blocks the drain due to an act of negligence, it's their responsibility. It is normally caused by something they've done. But it can be worth going the extra mile to be a good landlord and sort the problem out for tenants. And anyway, if the tenant has to pay over £100 to Dyno-rod, they may not be able to pay the next month's rent!

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