How To Unblock An Outside Drain

Having trouble with a blocked outdoor drain? Here is a guide to unblocking it.

Outside drains flush water from a home into the lateral drains in the road. 

Your home may have a kitchen drain mounted near the kitchen’s outside wall, which is the usual culprit if you notice a blockage. Some homes also have a larger drain in a front garden that flushes wastewater from showers, baths and toilets. 

Beware that drains on or near your property might be jointly owned if you live in a terraced or semi-detached house. 

If your drain is ambiguous and you’re not sure who’s responsible for it, ask your neighbours if they’re also experiencing a blockage. If so, unblocking the drain should be a collaborative effort!

This is a guide to locating your outside drain and ridding it of a blockage!

How to find your drain

Some homes have a small, exposed kitchen drain outside the property. Kitchen drains flush water from the kitchen sink and other appliances on your home's ground floor. Homes also often have drains in their front garden, which route wastewater from the house to the lateral drains in the street.

Blocked outside rain with two black pipes

They may also be connected to drainpipes. To work out how your drains work, switch your taps, showers and water-connected appliances on and off to discover where they exit your property. 

As mentioned, any drain on your property is probably your responsibility, but some are ambiguous. Ask your neighbours if you’re unsure. 

Once the drain exits onto the public highway, it’s owned by a local water company. 

Note - if your kitchen sink is blocked read this guide to help unblock it

Causes of a blocked outside drain 

If your outside drain is blocked, you’ll probably notice a buildup of water by the drain itself. The water will either drain slowly or inefficiently or overflow. Your drain may also smell, especially when water is flowing into it. 

Here are the top causes of a blocked outside drain: 

1: Build-up of sediment, debris and waste

Drains can become blocked by various sediment, waste and debris. Food waste is a common one, especially oil from washing up pans. It’s not recommended to pour hot or cold oil down the sink. 

2: Leaves and moss

Dead leaves can fall on top of the outside drain and catch over the strainer/grill. If the leaves then dry out and crumble or get wet and force their way through the grill, they’ll block the drain. Any accompanying dirt and other sediment worsen the problem. Moss buildup over the drain cover can also block it if the moss falls into the drain. 

3: Tree roots

If there are trees nearby the drain(s), these can become a significant problem over time. In addition, tree roots push through into the drain and block it, also exacerbating any other blockages.

4: Flushing solid items

If your outside drain is blocked outside the front of your house (the larger drain with a metal drain cover), it might’ve been caused by flushing wet wipes and other non-degradable items. 

Ways of unblocking an outside drain

If the blockage is superficial, e.g. moss is clogging up the strainer/grill, then removing the blockage may be as easy as removing the grill and cleaning it. The grill itself might have become worn or broken. 

Otherwise, follow the following steps for unblocking your outside drain: 

1: Remove the drain cover and inspect the drain 

Firstly, remove the cover and inspect the drain. If leaves, moss, and other organic debris is the cause, then this should be obvious. However, that doesn’t mean that there isn’t also a problem deeper in the drain. 

If the drain cover is broken or degraded, replace it when you’re finished cleaning the drain. 

Inspect the drain with a torch. If it’s overflowing, then this might be tricky - move on to the next step instead. 

2: Use a drain rod

A drain rod is a larger form of a plumber’s snake, a device used to unblock sinks and shower drains. Drain rods are fed into the drain until you feel the blockage, at which point you drill into the blockage and forcibly loosen it. 

Engineer in high viz unblocking outside drain with drain rod
Above: Long drain rod

To use a drain rod:

  1. Attach the drain rods. Keep feeding the drain rod into the drain while screwing rods onto the end as needed. 
  2. Once you feel resistance, start forcibly wiggling the rod to unblock the drain. 
  3. This takes trial and error. Feel the blockage through the rod and test the drain by pouring hot water down to see if it clears quicker. 

3: Bicarbonate soda 

If the drain rod fails, or if it only partially works, it’s time to start adding other substances to clear the drain. Bicarbonate soda and vinegar are the go-to. 

  1. Pour a cup of bicarbonate soda down the drain. 
  2. Add a similar quantity of vinegar. The solution should bubble up.
  3. Attack the drain with the drain rod. 

4: Hose or pressure washer 

You can also squirt a hose down the drain to clear it. Some power hoses are compatible with sewer jetters, which are nozzles fixed to the end of a hose that feeds down the drain. 

Be careful clearing a drain with a normal pressure washer, as you don’t want to crack or dislodge the pipes - that would create a bigger problem!

5: Use drain cleaning products 

You can use drain cleaning products to clear a stubborn drain. Outdoor drain unblockers should be labelled as suitable for outdoor drains, which means they’re probably stronger than inside drain cleaners. 

Follow the guidance and take extra care when using these products as they can be very nasty to the skin and eyes. Goggles and gloves are a must. 

If you don’t have specialist drain cleaning products to hand, washing powder and hot water might do the trick. Combine with your drain rod to melt blockages and force them out of the drain. 

When to call a plumber 

If your outdoor drain doesn’t clear with a drain rod and any attempt to unblock it with water or cleaning products results in more standing water, the blockage might be further down the drain. 

Engineer in high viz cleaning outdoor drain with hose outside red brick house
Above: Professional drain cleaning 

While attacking a drain with a drain rod is generally safe, being too forceful might break the drain, worsening the issue. The same applies to a pressure washer - you don’t want to crack or dislodge a pipe! If you keep having blocked drains, take a look at our drainage policies, which may give you that peace of mind.

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