Blocked drain outside: how to check and clear a yard gully

Outside drains in Sheffield’s older terraces take a lot of punishment. Back yards collect leaves and silt, downpipes carry everything off the roof, and kitchen waste brings fat and food. In streets that drop steeply down a hillside, as many do in Walkley, the shared drain behind the row can catch everything from the houses above. Here is how to work out where the blockage is and what you can do yourself.

Know what is outside

In a typical Sheffield terrace back yard you will find:

• A gully, a small square grate at ground level where the kitchen sink waste and sometimes a downpipe empties. It has a water trap below the grate.
• A downpipe from the roof, which may run into the gully or into its own drain.
• A soil stack, the large pipe from the toilet, running down the back wall into the ground.
• A manhole or inspection chamber, a metal or plastic cover giving access to the drain. In a terrace, there may be one in your yard, or one shared at the end of the row.

Step 1: lift the manhole

If you can do it safely, lift the nearest manhole cover. Use a proper lifting key or a strong flat bar under the edge. Keep fingers out from underneath, keep children and pets back, and never climb in.

• If the manhole is full of water, the blockage is downstream of it, further along the drain towards the sewer.
• If the manhole is empty or flowing, the blockage is upstream, between your gully or toilet and that manhole.

Step 2: check who else is affected

If the full manhole serves more than one house, or neighbours have slow drains too, the blockage is likely in a shared drain. Since 1 October 2011, drains shared by two or more properties, and lateral drains outside your boundary, have been the water company’s responsibility.

In Sheffield, that is Yorkshire Water. Its sewer flooding page says that if your neighbours are having similar problems, the blockage is probably in its sewers or pipes and it is its responsibility to fix it. Our post on when Yorkshire Water should clear a drain goes into detail.

Step 3: clear the gully

If the blockage is in your gully:

1. Put on thick rubber gloves.
2. Lift off the grate.
3. Scoop out leaves, silt, fat and food by hand or with a small trowel. Bag it for the bin.
4. Pour a bucket of water in to check it drains.

If the water still sits there, the blockage is in the trap or the pipe beyond.

Step 4: use drain rods

Drain rods are flexible rods that screw together, with a plunger or corkscrew head. You can hire or buy them.

1. Fit the plunger head first.
2. Push the rod into the drain from the manhole or gully, adding rods as you go.
3. Always turn the rods clockwise as you push and pull. Turning anticlockwise can unscrew them inside the pipe.
4. When you meet the blockage, push and pull firmly to break it up.
5. Run water to flush it through.

If plunging does not work, a corkscrew head can grab roots or rags.

What causes outside blockages in Sheffield terraces

Cause	Where it shows	What helps
Leaves and silt	Yard gullies, especially in autumn	Clear gully regularly, fit a leaf guard on the downpipe
Fat and food	Kitchen gully	Wipe pans before washing, use a sink strainer
Wipes and paper	Toilet drain, shared runs	Bin, not flush
Roots	Old clay pipes near trees	Camera survey, root cutting, lining
Sunken pipe	Steep slopes, old clay joints	Camera survey, repair or relining
Broken gully trap	Smell and slow draining	Replace the gully

Steep streets

On a steep hillside, a drain can drop sharply then level out. Solids carried down fast settle where the pipe flattens. Old clay joints can also shift on a slope, leaving a step where waste catches. That is why some houses in a sloping row block again and again. Our Walkley area page explains how pipes run in those hillside terraces.

When to call

Call a plumber or drain engineer if:

• Rodding does not clear it.
• It keeps coming back.
• You cannot lift the manhole safely.
• There is sewage in the yard or the house.
• You suspect roots or a broken pipe.

If it is a shared drain, call Yorkshire Water first. If it is your drain and keeps blocking, a CCTV camera survey shows the cause so the repair can be targeted. Our blocked drains page explains what happens on a visit.

Avoiding a bill you should not pay

Before paying a contractor to clear an outside drain, ask whether it serves more than one property. If it does, it is very likely Yorkshire Water’s to clear.

Send us a photo of the gully and manhole and tell us who else is affected, and we will tell you whether to call Yorkshire Water or book a visit.