Sump Pump Systems & Services
Your basement's first line of defence against flooding!
A sump pump system is one of the most cost-effective ways to protect a basement from flooding. When groundwater or rainwater starts to rise beneath the basement floor, it flows into a sump chamber, and the pump immediately discharges it outside the building. This stops water from flooding the floor and damaging anything stored there. At Crystal Damp Proofing & Basements Ltd, we design, install and service sump pump systems for homes and commercial properties across London and the South East.
Is a Sump Pump Worth It?
Yes. A sump pump on its own does not stop water coming through the walls, but it acts as a shield: it removes the water before it can build up and flood the basement. If you want to use the basement as a living space, gym, fitness room or office, however, a pump alone is not enough. It must work together with proper waterproofing.
Has Your Basement Flooded After Rain?
If water stands on the basement floor after rain, the groundwater level has risen above the floor, or rainwater cannot soak away fast enough and is finding its way into the building. Installing a sump chamber at the lowest point of the basement with an automatic pump is the quickest and most effective way to stop the floor flooding again.
Wet Walls After Rain: Pumps and Membranes Together
Wet walls mean water is pressing against the building from the side, through the ground. A drainage membrane on its own is not a waterproof layer. To keep the walls dry, it must be part of a complete system:
- Externally: we excavate around the foundations, apply proper vertical waterproofing (such as thick bituminous coatings), protect it with a studded membrane and lay perimeter drainage pipes at the base of the foundation. The pipes collect water from the walls and carry it to the sump, where the pump discharges it away from the house.
Internally: where excavation is not possible, we install a Type C cavity drain membrane with perimeter drainage channels that lead water to the sump and pump.
A Dry, Habitable Basement Needs Both
If the basement is to become a usable room, such as a gym, office or entertainment space, waterproofing and pumps must always work together:
- Waterproofing on the walls and floor: creates a watertight barrier that stops moisture getting into the basement.
- Drainage and pumps: reduce the water pressure against that barrier. The drainage collects water around the foundations and the pump removes it, so the waterproofing is not under constant pressure and does not start leaking after a few years.
Without waterproofing, the walls stay damp, which leads to harmful mould and fungi and plaster coming away, even if the pump runs non-stop.
Planning a gym or fitness space in your basement without a conversion? Please be aware. It is better to convert and extend the basement properly from the start than to run into problems later with ceiling height and room dimensions, or with Building Regulations. Together with our architects and engineers, we can plan the waterproofing, pumps and conversion as one project.
Where Should the Water Go?
The right discharge point protects your home from smells and backflow:
- Into a foul or combined sewer: the best option, but always via a trapped gulley, which stops sewer gases and smells coming back into the basement.
Into a surface water drain: connected directly, with a non-return valve fitted, so rainwater cannot flow back into the basement during a downpour.
Back-Up Protection
Most basement flooding happens during violent storms, which are often accompanied by power cuts. That is why we recommend:
- Battery back-up (UPS) or a generator: keeps the pump running during a power cut.
A second, back-up pump: professional systems use a twin-pump set-up, where the second pump starts if the first fails or if water comes in very fast.
Sump Pump Servicing
We recommend servicing your sump pumps twice a year, in spring before the thaw and in autumn before the heavy rain. Our service includes:
- Cleaning the sump chamber: we remove the pump and clear silt, sand and debris from the bottom of the chamber that could block it.
- Cleaning the inlet strainer: we clear any build-up from the pump’s intake.
- Checking the float switch: we make sure it moves freely and does not catch on the chamber walls or cables.
- Testing: we fill the chamber with clean water and check that the pump starts automatically and empties it quickly.
- Checking the discharge: we check the non-return valve and make sure the gulley trap is filled with water.
Musty Smell Around the Pumps? Book a Service Now
A smell of mould and damp in the pump room, or on the floors above, is an urgent warning sign. It means mould spores are already growing in the building and the drainage or ventilation is not working properly. The most common causes are:
- Stagnant water in the chamber: if the pump does not empty the chamber fully, for example because of a badly set float, silt, grease and bacteria build up, smell and release moisture into the whole house.
- Dry gulley or failed non-return valve: sewer gases and smells can come back into the basement.
- An overloaded pump: a blocked strainer or impeller means the pump cannot keep up, and humidity in the basement rises sharply.
During an urgent service, we isolate and remove the pump, clear out the remaining water and silt, clean and disinfect the chamber, clean the impeller and float, test the pump, refill the gulley trap and check that the smell barrier works. We then find the source of mould, checking behind furniture, the floor around the pump and the corners of the walls, and treat it with a professional fungicide.
Simply opening windows at this stage only spreads spores around the house. The source of the moisture must be removed first, and the affected areas treated.
Why Can You Smell It on the Floors Above?
A damp, mould-affected basement can affect the whole house, even in a three-storey building:
- The stack effect: warm air rises through the house and escapes through the roof or ventilation, drawing air from the basement upwards through gaps in floors, service openings and doors. Mould spores and toxins travel with it to the ground and upper floors.
- Capillary rise: if the basement walls stay wet, the masonry draws water upwards like a candle wick, sometimes up to the ground or even the first floor, bringing damp, salts and mould with it.
If you can smell mustiness upstairs, the concentration of spores in the air is already high and everyone in the house is breathing them in. This can lead to allergies, asthma, recurring infections, headaches and tiredness, especially in children and older people.
Mould and Fungi in Damp Basements
When basement humidity stays above 60–70%, two main groups of organisms develop:
- Dry rot (Serpula lacrymans): the most destructive fungus in buildings. It can carry water many metres through its strands, spreading even across dry masonry, destroying timber and weakening mortar.
- Wet rot (Coniophora puteana): appears where materials are constantly wet or flooded, causing brown rot.
- Aspergillus: a black or dark brown growth, one of the most common moulds in damp basements.
- Penicillium: greenish, fluffy patches.
- Black mould (Stachybotrys chartarum): grows on cellulose-rich materials such as plasterboard, wallpaper and damp insulation, and is considered one of the most toxic household moulds.
Qualified Specialists & a 10-Year Guarantee
Our family-run team holds CSSW qualifications, with a minimum of 10 years’ experience each. We back our work with a 10-year guarantee covering workmanship, plus a QANW Insurance Backed Guarantee that transfers to the new owner if you sell your property. Based in Croydon, we work on domestic and commercial properties across London and the South East.
See What Our Clients Say
We are proud of our 5-star Google rating: see our reviews. If your basement is damp or takes in water, book a survey in our Booking Survey section, or call or message our fully qualified advisors.
