New Build Drainage Problems Horsham | Spot Them Early

Your new house smells like a drain. Or the garden's waterlogged after a week of decent rain. Or the upstairs toilet gurgles every time someone runs a bath downstairs. You're six months into a brand-new property and something's already wrong underground.

I hear this more than you'd think. Littlehaven, Holbrook, parts of North Heath, the newer phases out towards Broadbridge Heath. Shiny houses, fresh tarmac, and drains that were never right to begin with.

Here's the thing most developers won't say out loud. Drainage is one of the last trades on site, it works in confined trenches alongside other services, under pressure to hit completion dates, and the inspector who signs it off isn't necessarily putting a camera down every run. Mistakes get buried. Literally.

What's Actually Going Wrong

I ran a CCTV survey on a two-year-old detached on the Littlehaven side of RH13 last spring. The owners had slow drains throughout and a wet patch appearing in the utility room floor. What we found was a combination I see on new builds regularly.

First, there was a displaced joint about four metres from the main stack. The pipe had settled, the rubber coupler had shifted, and ground water was infiltrating. Second, we had a partial blockage of building debris, mortar slurry specifically, that had set almost solid in a 90-degree bend. Third, the gradient on one run was virtually flat. Someone had laid it in a rush and hadn't checked the fall.

None of that would have shown up on a visual inspection from the manhole. You need a camera to find it.

The Building Debris Problem

Mortar slurry is the one that catches people by surprise. During construction, workers clean tools in or near drains. Cement wash, plaster water, floor-screed runoff, it all goes somewhere. If it goes down your new drainage system, it doesn't flush out clean. It coats the inside of the pipe, reduces the bore, and in bends it accumulates. Give it a few months and you've got a partial blockage that behaves like a full one when three people are showering at the same time.

High-pressure water jetting will shift most of it. Some of the harder set material needs a bit more persuasion. But the real question is whether it's damaged the pipe wall underneath. That's when a CCTV survey earns its money.

Shared Private Sewers: The Part Nobody Explains

A lot of new estates in Horsham run on shared private sewers. That means the pipe leaving your property might serve three, five, or ten other plots before it connects to the public sewer. Everyone's waste travels through everyone else's drainage.

The legal picture shifted in 2011 when many private sewers transferred to Thames Water, but plenty of the newer adopted layouts still have private shared sections that haven't transferred, or won't. Your solicitor may have flagged this in the deeds. Most buyers don't read that section carefully.

What it means practically: if the shared section blocks or collapses, no single homeowner is automatically responsible for fixing it. You need to agree with your neighbours, find out who owns it, and either chase the developer (if it's within the liability period) or deal with it collectively. I've seen this turn neighbourly by autumn and ugly by Christmas.

If you're on an estate in RH12 or RH13 and you're not sure what's shared and what's yours, a CCTV survey with a drainage plan overlay will tell you exactly where your responsibility ends.

The Developer Sign-Off Gap

Builders complete, building control signs off, you get your keys. What most buyers don't realise is that NHBC or similar warranty cover doesn't automatically mean someone has inspected your drains to the standard a proper drainage engineer would. The structural warranty covers the structure. Drainage defects are often in a grey area unless they cause immediate and obvious damage.

You've typically got two years to report defects to the developer for remediation under the standard new build warranty. After that, the costs fall to you. I've had calls from homeowners in Littlehaven and on the Holbrook estate who've been sitting on a slow drain for eighteen months, assumed it was normal, and then rung me after the two-year window closed. That's an expensive assumption.

Get a drainage survey done in your first year. Not because something is definitely wrong. Because if something is wrong, you want to find it while the developer still has to fix it.

What a CCTV Survey Actually Shows

A lot of people think a drain survey is just checking for blockages. It's more than that.

• Pipe gradient and whether water will drain freely or pond
• Joint displacement and root ingress points
• Debris accumulation, including construction mortar
• Pipe deformation, meaning the pipe has been crushed or distorted by ground pressure or poor bedding
• Cracking, fractures, open joints where ground water gets in
• Whether the drain is laid to the correct plan, not all builds match the spec

We produce a written report with footage reference points and a condition rating. That's the document you hand to your developer, or your solicitor if it goes further.

Soakaway Issues on Newer Plots

Surface water on new-build plots in and around Horsham is increasingly managed through soakaways or attenuation systems rather than connecting to the sewer. Good in principle. Variable in practice.

I've seen soakaways installed in ground that simply won't drain. The percolation test should identify this before design, but it doesn't always happen properly. The result is a garden that holds water, a soakaway that backs up, and sometimes surface water finding its way to the house rather than away from it. If your lawn looks like a pond two days after rain, the soakaway is the first thing worth investigating.

What I'd Tell Any New-Build Buyer in Horsham

Don't wait for a symptom. If you've moved into a new build in the last two years, anywhere from Littlehaven to Southwater to Billingshurst, book a CCTV survey before your snagging period expires. It's not dramatic. It's just sensible.

If you've already got symptoms, slow draining, gurgling, wet patches, bad smells with no obvious cause, ring us rather than waiting to see if it clears. Building debris blockages don't clear themselves. Displaced joints don't reseal. A small problem surveyed and fixed in year one is a very different bill to a collapsed shared sewer in year four.

Drainsco covers Horsham and the RH postcodes, engineers available around the clock, no call-out fee, and a clear price before any work starts. On drain repairs and relining we back the work with a 20-year guarantee. Give us a ring and we'll tell you straight what we're dealing with.