Tanks that stop leaking into the slab and stop shedding old coating into your water.
Overhead tanks and sumps drained, chipped back, repaired at the joints and coated internally with a system suitable for stored water, so the tank stops weeping into the structure and stops shedding old coating into your supply.
- Free site inspection
- Written, itemised quote
- 1-year workmanship warranty
- Same-day callback
At a glance
What does water-tank waterproofing actually involve?
It's waterproofing applied inside the tank, not outside. The tank is drained, cleaned, chipped back to sound concrete, cracks and honeycombed patches repaired, fillets formed at every corner, then a coating suitable for stored water applied across the walls, floor and lid soffit. Coating from inside works with the water pressure instead of being pushed off by it.
When this is the answer, and when it is not.
Sending you to the wrong service wastes your money and our time. This is how to tell.
This is likely right if
- The ceiling or wall directly below an overhead tank is staining or blistering
- The old coating inside the tank is chalking, blistering or coming away in flakes into the water
- A new tank or sump is built and you want it coated before it is ever filled
- A sump is taking in groundwater, or its walls stay wet on the outside face after it is emptied
Something else comes first if
- The tank wall is cracked through and moving, or the reinforcement is exposed and rusting, that needs a structural engineer's opinion and concrete repair before any coating goes on
- The leak is actually from the inlet, overflow or outlet pipe joint rather than the tank body, a plumber should isolate and fix that first, or the new coating will be blamed for a plumbing fault
- The tank can't be taken out of service and left empty for the full preparation and curing period
What the service includes.
Tank inspection and system selection
We inspect the tank empty and dry, walls, floor, lid soffit, pipe entries and the outside face for damp patches, then choose a system suitable for potable storage or for a sump, whichever the tank actually is.
Draining, desilting and cleaning
The tank drained and pumped out, silt and biofilm removed, and old chalky or blistered coating chipped back to sound concrete so the new system bonds to the substrate and not to a failing layer.
Crack and honeycomb repair
Cracks cut out in a V, honeycombed patches opened up, and both packed with polymer-modified repair mortar. Any leak that runs under pressure is plugged before coating starts.
Corner fillets and pipe entries
Coved fillets formed at the floor-to-wall and wall-to-wall junctions, and pipe penetrations, washout and overflow entries sealed, Coved fillets formed at the floor-to-wall and wall-to-wall junctions, and pipe penetrations, washout and overflow entries sealed, a flat wall is one continuous surface, while every junction and every pipe entry is a break in it that the coating has to bridge.
Coating application
Applied to the whole internal surface including the floor and the underside of the lid, in the coat count and film thickness the system requires, with each coat allowed to cure before the next.
Curing, flushing and handover
The tank left to cure for the stated period, then flushed and drained before refilling, with the system used, coat count and care instructions written down for you.
Not included, or quoted separately
- Plumbing work, inlet, outlet, overflow and washout pipe replacement, valve and float repair
- Structural repair of a cracked or spalling tank wall, and any work needing a structural engineer's opinion
- Water testing of potability, or any laboratory analysis of stored water
- Desilting and cleaning of a tank we aren't coating, and disposal of accumulated sludge beyond our own debris
- Waterproofing of the terrace slab the tank sits on, or the sump surround, quoted separately
The sequence.
Inspection with the tank empty
We look at a drained tank, not a full one. Wall condition, floor, lid soffit, pipe entries and the outside face are all assessed, and the damp patch on the ceiling below is traced to where it actually starts.
Agree the shutdown sequence
Which tank goes out of service first, how the building draws water meanwhile, and where the drained water goes. For a single-tank home this is the part that needs planning, not the coating.
Drain, clean and chip back
Silt and biofilm removed, old coating chipped off, and the surface keyed. Debris is bagged and taken out rather than washed into the drain.
Repair and seal
Cracks and honeycombing cut out and filled, fillets coved at every junction, pipe entries sealed. Nothing gets coated until the repairs have set.
Apply the system
Coats applied to the specified thickness across walls, floor and lid soffit, with proper lighting and forced ventilation inside the tank throughout.
Cure, flush and refill
The coating cured undisturbed, then the tank flushed and drained before it goes back into service. We hand over a written warranty with its conditions stated, and tell you what will void it.
What moves the price on this job.
We do not publish a rate, because it would change once someone measured your property. These are the variables that decide it.
- Tank capacity and internal surface area, measured wall by wall including the floor and the underside of the lid
- Whether the tank is overhead, at ground level, or a below-ground sump, which decides access, lighting and ventilation
- Existing coating that has to be chipped off and disposed of, and how well it is stuck
- Condition of the plaster inside, patchy hollow render pushes the job towards a full re-render before coating
- Number of pipe entries, ladder rungs, lid seatings and corner junctions needing fillets and sealing
- Whether the tank is one of a pair that can be emptied in turn, or the only supply, which changes the working sequence
Water-Tank Waterproofing — your questions.
Can the tank stay in use while you work?
No. The tank has to be fully emptied, cleaned and dried before anything is applied, and it must stay empty while the coating cures. If the tank is your only storage, plan for an alternative supply or arrange for the sump and overhead tank to be done at different times. We agree the sequence with you at the inspection so the building is not left without water unexpectedly.
Is the coating safe for drinking water?
We only use systems the manufacturer states are suitable for potable water storage, and we apply them at the stated film thickness with the stated curing and flushing before the tank is refilled. Coatings meant for terraces or basements aren't appropriate inside a drinking water tank, whatever they cost. We'll name the system on your quotation so you can check it yourself.
Water is seeping through the tank wall. Will coating the inside stop it?
Often yes, because coating the inside works with the water pressure rather than against it. But if the leak is through a live structural crack that opens and closes, a coating alone will split again. In that case the crack is cut out, filled and bridged first, and if it is moving because of the structure, you need a structural opinion before we coat.
Why chip off the old coating instead of coating over it?
A new coat bonds only as well as the layer beneath it holds to the concrete. A coating that has been submerged, then drained and refilled again and again, goes chalky, blisters or lifts in sheets, so anything applied over it peels off with it, into your stored water., so anything applied over them peels off with them, into your stored water. We remove loose material back to sound concrete and key the surface so the new system grips the substrate itself.
What about the underside of the lid and the ladder?
The lid soffit is where condensation collects and The lid soffit sits over still, saturated air, so condensation forms on it and stays there, that's where black growth and rust staining show up, and it gets the same treatment as the walls., so it gets the same treatment as the walls. Fixed metal ladder rungs are cleaned back and coated, or noted for replacement if they have corroded through. Anything we think is beyond coating is written down rather than covered up.
Related services
- Terrace WaterproofingThe slab an overhead tank sits on takes the same water, worth checking while the tank is empty.
- Waterproofing and ProtectionSee how terrace, exterior wall, bathroom and tank systems differ before choosing.
- Dampness and Seepage TreatmentFor the stained ceiling or wall the tank has been wetting from above.
Let us look at your walls first.
Tell us about the property and we will set up a free colour and wall inspection. You get a written, itemised quotation afterwards, with no obligation to go ahead.
- We call you back the same day to get a picture of the property and the surfaces.
- We agree a time and come out for the free inspection.
- You get the written scope and itemised quotation.
- Nothing starts until you approve it.