Blocked Downpipe or Blocked Drain? Where Rainwater Is Actually Stuck

The Water Is Going Somewhere It Shouldn’t. But Where, Exactly?

You’ve got water pouring down the outside of your house, pooling against the wall, or bubbling up from a gully in the garden. Something is blocked. The question, before anything else, is where the blockage actually is, because the answer changes what you do next.

There are three distinct places rainwater can get stuck, and they behave quite differently.

---

The Three Suspects

1. The Downpipe Itself

The downpipe is the vertical plastic or cast-iron pipe that carries rainwater from your gutters down to ground level. Leaves, moss, tennis balls, and the occasional pigeon nest are all enthusiastic participants in blocking these.

What you’ll see: Water overflowing from the gutter above the downpipe connection, or a visible bulge or split in the pipe itself. The pipe may gurgle or drip from joints rather than flowing cleanly at the bottom outlet.

Safe ground-level check: Look at the bottom of the downpipe where it meets the gully (the small square or round drain at ground level). Is water coming out of the pipe at all? If nothing is emerging during heavy rain, the blockage is likely higher up in the pipe or at the hopper head where the gutter feeds in.

We are not going to tell you to climb a ladder. That is a job for a guttering specialist, and it is not what Drainiacs does. If the blockage is above head height, call a guttering or roofing contractor.

2. The Gully

The gully is the ground-level drain that receives water from the downpipe and from yard or path surfaces. It sits in a small pot or trap, and that trap is designed to hold a small amount of water as a seal against smells. It is also, professionally speaking, a magnificent collector of silt, leaves, moss, and general garden debris.

What you’ll see: Water backing up and overflowing at ground level around the gully grid, even though the downpipe above it appears to be flowing fine.

Safe ground-level check: Lift the gully grid (they usually lift straight out). Look inside. If you can see a solid mat of debris sitting in the pot, that is your blockage. A gloved hand and a bucket can clear a shallow gully trap in a few minutes. If the pot looks clear but water still won’t drain away, the problem is further underground.

3. The Underground Rainwater Drain

This is where it gets more interesting. Beneath your garden or driveway, rainwater drains run to a soakaway (a buried pit that disperses water into the surrounding soil) or connects into the surface-water sewer. These pipes are typically 100mm diameter, and they are just as capable of blocking or collapsing as any other underground drain.

What you’ll see: The gully pot is clear, the downpipe is flowing, but water still backs up and overflows. Or you notice a section of lawn that is permanently waterlogged even in dry weather.

This is the point where the puzzle gets genuinely good.

---

When It’s Underground: What Happens Next

If ground-level checks don’t find the blockage, the drain needs investigating from below. The standard approach is a CCTV drain survey, where a small camera is fed along the pipe to find exactly what is going on (think: nature documentary, but the wildlife is tree roots and collapsed clay pipe).

Common findings in older TW properties include:

• Root ingress: Tree roots, particularly from willows, poplars and older fruit trees, push through pipe joints and eventually block the flow entirely.
• Silt and sediment build-up: Rainwater drains carry grit and fine soil. Over years, this settles and narrows the pipe.
• Collapsed or deformed pipe: Older clay or pitch-fibre pipes (pitch-fibre is a compressed cardboard-and-tar material used in many post-war properties, and it eventually deforms under load) can partially collapse, restricting flow even when there is no physical blockage.
• Soakaway failure: A soakaway that has silted up or become saturated in clay-heavy ground will back up into the drain above it.

A CCTV survey typically costs in the region of £150 to £300 for a residential drain, depending on access and length. If a blockage is found and cleared in the same visit with a high-pressure water jetter, expect the combined cost to be broadly in the £200 to £400 range. These are indicative figures; any reputable company will give you a fixed price before work starts.

---

A Quick Decision Guide

What you observe	Most likely location	First step
Gutter overflowing above downpipe	Gutter or hopper head	Guttering contractor (not a drain company)
Downpipe not flowing at all	Downpipe blockage	Guttering contractor
Gully overflowing, pot full of debris	Gully trap	Clear the gully pot yourself
Gully pot clear, water still backs up	Underground drain	Call a drainage company
Lawn waterlogged near soakaway	Soakaway failure	CCTV survey and assessment

---

One Thing Worth Knowing About Surface Water and Insurance

Persistent rainwater flooding that enters a property, rather than just pooling outside, is a different matter. If you are dealing with water inside the building, you should check your home insurance policy before any work begins, as some policies cover drainage investigation and reinstatement. For guidance on water damage and what to do when flooding affects the inside of a property, Emergency Plumbers TW has a useful overview.

---

When to Call Drainiacs

If your ground-level checks haven’t found the problem, or if water is backing up persistently after every rainfall, the blockage is almost certainly underground and needs professional equipment to locate and clear it.

Drainiacs cover the full TW postcode area, including Twickenham, Richmond, Hounslow, Feltham, Ashford, Staines, Shepperton, Sunbury, Hampton, Teddington, Whitton, Isleworth and Brentford. We are available around the clock, every day.

If you need help now, call 07700 137648.