TL;DR
A gully that backs up after heavy rain usually means the drains are struggling to cope. A blockage, water pushed back from a full public sewer, or a pump that cannot keep up could each be the cause. Basement and lower-ground flats sit below street level, so they feel the problem sooner than upstairs flats. If you see standing water or slow drains, request a free quote online and we will talk through what is happening.
Reading the early signs
A slow gully, a shower tray that will not clear or a gurgling waste pipe after rain deserves attention. These signs are not dramatic. Still, in a below-street-level flat they often warn that the system is reaching its limit. Standing water in a lightwell points the same way, as does water at a floor drain while nobody is running a tap.
If only one fixture is slow and it clears with rodding, you may have an ordinary blocked drain. However, a problem that keeps returning after rain rarely fixes itself. It tends to come back worse the next time.
Why below-street-level flats are more exposed
Brighton and Hove has many Regency and Victorian terraces split into flats. In some of them the lower rooms sit below the sewer in the street. Two things then work against you.
First, a public sewer can fill up in sustained heavy rain. If your drain connects below that rising water level, the flow can push back towards your flat instead of away from it. Many people call this backflow. It does not need flooding in the street for this to happen.
Second, many of these flats use a pumped waste system to lift wastewater up to the sewer. A Saniflo-type macerator unit is a sound answer to a hard retrofit. However, it adds a moving part that can jam, stall or lose power just when the rain is heaviest. Our guide to Saniflo units that will not flush explains the common faults.
Non-return valves and CCTV checks
A non-return valve lets water flow out as normal, then closes if the flow reverses. It can lower the risk of backflow, but it is not a guarantee. A very severe event can overwhelm any valve, and a blocked valve brings its own problems. Treat it as one part of the answer.
A CCTV drain survey is the other part. A camera can show a partial blockage, roots or a damaged pipe that makes a bad situation worse. Our article on what a CCTV drain survey shows covers this in more detail. For anyone buying a flat like this, the homebuyer drainage survey guide is worth a read.
The landlord and managing-agent angle
Lower-ground flats are cheaper to look after before trouble starts. If a flat relies on a pump or macerator, keep a simple note of when someone last checked it. Tell tenants to flush only toilet paper and human waste, because wipes are a common cause of jams.
Where one drain serves several flats, a restriction usually affects everyone at once, so a periodic camera check makes sense. Our landlord plumbing service covers routine checks alongside repairs. See also our advice on landlord plumbing repairs in Brighton rentals.
What to do if it is happening now
Stop using any fixture on the affected drain or macerator, because more water into a backing-up system makes the mess worse. Note when it started, whether it followed heavy rain and whether one fixture or several are slow, because that helps us bring the right kit first time.
We help with flooded and slow drains in Preston Park area, with basement flat problems in Kemptown and with drain help in Hove. Request a free quote online and give us those details.
Frequently Asked Questions
Why does my basement flat flood when it rains heavily, even though nothing is blocked? If your drain connects below the water level in the public sewer, heavy rain can push water back towards you. This is a feature of the building rather than a fault in your pipes.
Does a non-return valve guarantee my flat will not flood? No. It reduces the risk, yet a severe event can still beat it, and a blocked valve can cause trouble. Think of it as one layer of protection.
Who is responsible, the landlord or the tenant? That depends on the cause and on the tenancy agreement, so we cannot give one answer for every flat. Tell your landlord or agent promptly, and keep notes and photos.
Can a CCTV survey help if the flooding seems weather-related? Yes. A survey can show whether a partial blockage or damaged pipe is making a weather-related backflow worse than it needs to be.
