Ask any contractor who handles landlords’ drain call-outs around Watford which addresses they know by heart and the answer is a short list of rentals. The ones where the same drain blocks in the same month, year after year, with a different tenant’s name on the job sheet each time. Watford has more of these than its size suggests, and the reason is the stock, not the tenants.

This piece is for a landlord who owns one of them. It sets out why the pattern happens, what the repair obligation covers, and what can be done between one tenancy and the next, because that gap is the only time the work is cheap.

Why Watford blocks on a calendar

The town’s rental stock splits three ways. The Victorian terraces around the centre and West Watford were built with a single clay drain per house, often running under the back garden to a shared pipe behind the row. The interwar semis that spread out along the Metropolitan line in the twenties and thirties have longer runs, gardens with mature trees, and joints that were made by hand with cement. The newer estates towards Abbots Langley and Kings Langley have shallower plastic runs under private roads and drives.

Each type fails in its own way, and each has a season. The terraces block on fat: a house share with one kitchen and a length of Victorian clay laid for a single family. Grease cools in the pipe from October, and the first heavy weekend of cooking in December is usually the call. The semis block on roots. Lime and plane roots grow into the joints in spring, and the blockage shows in the wettest weeks of winter when there is more water trying to get past the root mass. The newer estates block in heavy rain, when a gully laid too shallow backs up and the tenant reports a flooded drive.

If three years of invoices for the same address cluster in the same month, that is the season, and it tells a landlord the cause before anyone puts a camera in.

What the obligation actually is

Under section 11 of the Landlord and Tenant Act 1985 the landlord keeps the structure and exterior of the dwelling in repair, and the Act names drains, gutters and external pipes specifically. That covers the run from the house to the point where it leaves the property boundary or joins another property’s drain. Beyond that point the position changed in October 2011, when shared drains and the sections of private pipe outside the boundary were transferred to the water and sewerage companies. For Watford that means Thames Water. A collapsed pipe under the pavement, or a blockage in the shared run behind a terrace, is theirs to clear, and they will, provided someone tells them with a survey report rather than a phone call.

Tenants have obligations too. Fat in the sink and wipes in the loo are tenant-caused, and the cost can be recharged if the evidence is there. In practice it rarely is, because nobody photographed the drain at check-in and the invoice says “blockage cleared” and nothing else. So the landlord pays for most call-outs by default, including the ones that were never theirs. Ten minutes with Happy Drains’ who-is-responsible checker before the next invoice is argued over settles most of it.

The six weeks that matter

The void period is the only time a landlord controls access without a tenant in the way, and it is the only time a repair costs what it should. Four things are worth doing in it, in order.

First, read the reports. If the contractor has been giving one-line invoices, ring them and ask what they actually found and where. Fat at two metres is one problem. Roots at nine metres under the garden is another, and scale narrowing the whole run is a third. The answer decides everything that follows.

Second, jet the whole run once, properly. On a terrace that means from the kitchen gully to the shared pipe behind the row, not a quick clear from the gully that pushes the deposit along and buys six weeks. Ask for it by name.

Third, camera it if the pattern is longer than two years. A CCTV survey costs more than a jet, but it answers the question for good, produces a written report with the location and the material, and is the document that gets Thames Water to attend when the fault is on their side of the line. It is also the document that makes a tenant recharge stick.

Fourth, photograph the gullies and the kitchen trap at check-in, with the date, and put them in the inventory alongside the oven and the carpets. Two lines in the welcome pack about fat and wipes do more than any clause in the tenancy agreement, because a tenant who has been told the drain is Victorian does not want to be the one who floods the kitchen.

When the void is not the fix

Some of what a survey finds will not be solved by a clearance. A displaced joint on an interwar run, or a length of clay that roots have opened up every spring for a decade, needs relining or a short excavation. That is a landlord cost, but it is a one-off cost that ends the cycle, and it is much easier to justify with a survey and a log of five clearances than on its own.

A firm that covers the town’s rentals will have seen the same address type many times, and the useful question to ask them is not what the emergency costs but what stops it. The good ones will quote fixed, upfront pricing with no hidden fees for both, and the landlord can set the two numbers against the invoice history.

The cycle breaks when someone looks for the cause instead of clearing the symptom. In most Watford rentals that is one survey and one proper clearance, paid for by the first winter that passes without a call.

Laurie Poulter, Website & Marketing, Happy Drains