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How to Unclog a Drain
Something is draining slowly, or not at all, and you are standing over it working out whether this is twenty minutes of your evening or a phone call. Most of the time it is the twenty minutes. This is the order a drainage engineer would try things in, and the point at which we would stop and get the camera out.
The Short Answer
Work from the fitting nearest the blockage outwards, and go cheapest first: plunger, then a hand auger, then rods. If only one sink or bath is slow, the blockage is in that trap or the short run behind it and a plunger usually shifts it. If several fittings back up at once, or the outside gully is standing full, the blockage is in the shared run and rods are the tool. Chemicals are near the bottom of the list for a reason.
First, Work Out Where The Blockage Actually Is
This is the whole job, really. Everything after it is just picking a tool. A blocked drain tells you where it is if you run the taps and watch what happens, and thirty seconds of that saves you an hour of poking at the wrong end.
If one fitting is slow and everything else in the house runs away fine, the blockage is in that fitting's own trap or the short length of pipe behind it. That is the easiest version of this problem and it is usually hair and soap in a bathroom, or fat and food in a kitchen. If two or more fittings back up together, especially if the downstairs ones go first, the blockage is further along where those pipes have joined into one. And if flushing the toilet makes water rise in the shower tray, stop what you are doing, because that is the main run and it needs rods rather than a plunger.
Outside, lift the grid on the gully by the back door and look. A gully that is standing full of water has a blockage below it. A gully that drains away but smells is usually just a trap full of silt and leaves that wants cleaning out. Those are two different jobs and it is useful to know which one you have before you start.
One more check that costs nothing. If you share a back court or a close with other flats, ask whether anyone else has the same problem this week. A blockage affecting three flats is in the shared run, and that changes both the tool and, often, who is paying for it.
The Order To Try Things In
Cheapest and least destructive first, every time. Each of these takes a few minutes and each one rules something out, so even when a step does not clear it you have learned where the problem is not.
- Hot water, not boiling. A kettle of hot water down a kitchen sink will soften a fat blockage enough to move it. Use hot rather than freshly boiled if the run is plastic waste pipe, because boiling water straight from the kettle can distort thin uPVC and soften the compression seals on a trap, and a leaking trap is a worse problem than a slow sink.
- Empty the trap by hand. The U bend under a sink unscrews by hand in most cases. Bucket underneath, unscrew both collars, and tip out what is in there. On a bathroom sink this clears it perhaps half the time and you will see exactly what caused it, which is worth more than the fix.
- Plunger, with the overflow blocked. The bit people miss: a sink has an overflow slot and if you do not hold a wet cloth over it, most of your effort goes up there instead of down the pipe. Cover the overflow, get a proper seal on the plughole, and use short sharp pushes rather than one long shove.
- Hand auger, sometimes called a drain snake. About fifteen quid from any merchant and the single most useful thing a homeowner can own for this. Feed it in until it stops, turn the handle to bite into whatever is there, then pull back slowly. You want to pull the blockage out, not push it further into a wider pipe where you cannot reach it.
- Rods, for anything past the gully. This is where the outside job starts and it gets its own section below.
How to Rod a Drain Without Losing the Rods
Rodding is not difficult and it is not glamorous. A set of drain rods is about twenty five pounds and they screw together end to end, so you can push a head fifteen or twenty feet along a pipe from an access point. The technique matters more than the strength.
The rule that saves you a miserable afternoon: always turn the rods clockwise, and never let yourself turn them the other way while they are down there. The sections screw together clockwise, so turning anticlockwise unscrews them, and you will pull back a short length of rod and leave the rest of the set sitting in your drain along with the blockage. Recovering those is a much bigger job than the one you started with.
- Find your access. Usually a round or rectangular inspection chamber cover in the back court, path or garden, or the gully itself. Lift it with a screwdriver or a proper cover key, and take a look before anything else goes in.
- Read the chamber. If the chamber is full, the blockage is downstream of it, so rod towards the sewer. If it is empty and dry but the fittings inside are backing up, the blockage is upstream, so rod back towards the house. This one observation decides which way you go.
- Start with two or three rods and a plunger head. Push, do not hammer. Add a rod at a time as you get further in.
- Turn clockwise the whole time, even when you are just pushing. It becomes automatic after a minute and it is the difference between a cleared drain and a very bad afternoon.
- When you feel it give, keep rodding past it and then run the taps hard for a couple of minutes to flush the debris through rather than leaving it to settle somewhere else.
- Wash the rods, wash your hands properly, and put the cover back on straight. A cover left proud is a trip hazard and, in a shared back court, somebody else's ankle.
What Drain Unblocker Actually Does, and What It Does Not
Chemical drain unblocker is usually sodium hydroxide, caustic soda, sometimes with bleach in it. It works by generating heat and turning fat, hair and organic matter into something soft enough to wash away. Against those things, in a small domestic waste pipe, it genuinely does work.
It does nothing at all to the things that cause most of the blockages we actually get called to. Wet wipes do not dissolve, and the packet saying flushable refers to whether it leaves the toilet, not whether it makes it to the sewer. Tree roots do not dissolve. Silt and grit do not dissolve. A cracked, bellied or collapsed pipe is not a blockage at all, it is a defect, and no amount of anything poured down it will change the shape of the pipe.
So the honest position is that unblocker is worth one go on a slow kitchen or bathroom waste, and worth nothing on a drain that is completely stopped or that keeps blocking in the same place. Pouring a second bottle after the first did nothing is the point at which people usually create the actual problem, because you now have a pipe full of caustic solution that has to come out before anyone can safely put a hand or a rod into it. Tell whoever comes out what you have used. Paul would much rather know than find out.
The kinder version that nobody sells: a handful of soda crystals and hot water once a month down the kitchen sink keeps fat moving and costs about a pound. It will not clear a blockage. It stops a lot of them starting.
Clearing an Outside Drain or Gully
The gully is the open drain at the base of a downpipe or outside the back door, with a grid over it. It has a trap in the bottom, the same as a sink does, and that trap fills with grit, leaves, moss off the roof and whatever the wind brought in. Cleaning outside drains is mostly this, and it is not a skilled job.
Lift the grid. Gloves on, and reach down into the trap and pull out what is in there by hand or with a small trowel. It will be unpleasant and it will be quick. Then flush it hard with a hose and watch how fast it goes away. Clearing an outside drain pipe that has silted up rather than blocked is often nothing more than this.
If the water sits there and will not drop, the blockage is past the trap and you are into rodding. If it drains but comes back within a day or two, something further down is only partly clear and it is filling back up, which is a different signal and usually means the run needs jetting rather than rodding.
Worth saying plainly because people ask: on a shared back court, who is responsible for a drain serving several flats is not always obvious, and it changes who pays. If your building is factored, a quick call to the factor before anyone starts work is sensible. We will always tell you where we think the boundary sits, but the factor holds the paperwork.
When It Blocks Again in the Same Place
A drain that blocks once is a drain that had something in it. A drain that blocks three times in the same spot is a drain with something wrong with it, and clearing it a fourth time is money spent on a symptom.
The usual causes, in roughly the order we find them. Root ingress, where a root has found a hairline crack at a joint and grown into the pipe, which then catches everything passing. A bellied run, where the ground has settled and left a dip that holds water and silt. A displaced or open joint, common on old clay. Or something solid that never left, a build up of scale, or debris left behind after building work.
This is the point where guessing gets expensive, and it is the point at which a camera earns its money. Half an hour with a CCTV drain survey tells you which of those it is, exactly how far along the run it sits, and whether the answer is a jet, a patch liner or a dig. That is the difference between one repair and four clearances, and it is the same argument as diagnosing a boiler down to the one faulty part instead of fitting three.
Drains in Glasgow Buildings
Most of the drainage we work on in this city was laid before 1919 and a lot of it is salt glazed clay in short lengths with mortar joints. It is good pipe, and plenty of it is still doing its job a hundred and twenty years on. Its weakness is the joints, which is where roots get in and where ground movement shows up first.
Tenement back courts are the specific case. One run often serves a whole close, so a blockage is rarely one household's problem, and the access chambers are frequently under whatever the back court has become since, which might be bin stores, a drying green, or a slab someone laid in 1985. Sycamores and privet along back court walls are the commonest root source we find, and they do not need much of a gap.
Newer housing has a different profile rather than no problems. Estates around Newton Mearns, Bishopbriggs and East Kilbride are plastic pipe with sealed joints, so roots are rare, but the runs are longer and shallower and they belly where the ground has settled over made up land. Kitchen extensions with a long waste run to reach an existing stack are a recurring one across the whole city, because a nearly flat run of pipe silts up no matter what it is made of.
The wipes problem is universal and it is the single biggest change in this trade over twenty five years. It has not got better. If there is one thing in this guide worth acting on before anything blocks, it is that.
When to Call Someone Out
Call when the water is not going anywhere and rods have not moved it, when more than one property is affected, when sewage is backing up into the building, or when the same drain has blocked more than twice in a year. The first three are a same day job and blocked drains is one of the services we run 24/7, because a back court filling with foul water at nine on a Sunday night does not wait until Monday. The fourth is not urgent at all, and it is the one where booking a survey rather than another clearance saves you money. Paul leads the drain team and Kyle runs the high pressure jetting, and between them they have been down most of the back courts on the south side at some point. You will get a clear price before any work starts, and that price is what goes on the invoice.
Blocked Drains in GlasgowCommon Questions
Hot water helps with fat and grease in a kitchen waste and does very little to anything else. Use hot rather than straight off the boil where the pipework is plastic, because water at a hundred degrees can distort thin uPVC and soften the seals in a compression trap. A kettle of hot water plus a squirt of washing up liquid, left ten minutes, is a reasonable first try on a slow kitchen sink.
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