Water Tank Filter for Overhead and Sump Tanks: What It Does and Does Not Do

A water tank filter is a sediment filter fitted at the inlet or outlet of an overhead or sump tank. It keeps sand, silt and rust out of the tank and your pipes, which protects taps, geysers and washing machines, but it does not remove microbes, dissolved salts or chemicals. For drinking water you still need a point-of-use purifier, and the tank itself still needs regular cleaning.

Why Overhead and Sump Tanks Get Dirty

Most Indian homes store water twice: a sump or underground tank fed by the municipal line, borewell or tanker, and an overhead tank that feeds the taps by gravity. Both collect:

• Sediment: sand and silt from borewells, tankers and old municipal lines settle as sludge on the floor.
• Rust and scale: flakes from iron pipes and pumps.
• Organic growth: algae where light gets in, and biofilm on wet walls.
• Things that fall in: dust, leaves, insects and, in a badly covered tank, worse.

A filter helps with the first two. It does nothing for the last two, which are the reason tank cleaning and a lid that fits matter as much as any filter.

Types of Water Tank Filter

Type	How it works	Good for	Upkeep
Spin-down sediment filter	Water spins through a mesh screen in a clear bowl; heavier particles drop to the bottom	Sand and grit from borewell and tanker water	Flush the bowl through its valve; rinse the mesh
Whole-house cartridge filter	A sediment cartridge in a housing on the main line, usually after the pump	Finer silt and rust across the house	Replace the cartridge when it clogs and flow drops
Inlet mesh or bag filter	A simple screen or bag over the inlet pipe inside the tank	Coarse debris, leaves, insects	Shake out and wash often
Multi-media tower filter	A tank of sand or other media, sometimes backwashed	Larger buildings and heavy sediment loads	Backwashing and media replacement; usually professionally serviced

Iron is a special case. If your water turns yellow or brown after standing, or stains buckets orange, iron is likely above the BIS IS 10500 limit of 0.3 mg/L, and a sediment filter will only catch the iron that has already formed particles. A dedicated iron removal filter is the right tool.

Where to Fit It: Inlet or Outlet

• On the inlet to the overhead tank (on the pump’s delivery line): sediment never reaches the tank, so it stays cleaner for longer. The filter must handle the pump’s pressure and flow without starving the tank.
• On the outlet from the overhead tank (the line that feeds the house): protects pipes and appliances from whatever has settled in the tank. Gravity pressure is low, so choose a filter with low resistance or flow at the taps will drop.
• At the sump inlet: a coarse mesh or bag catches the worst of tanker and municipal debris before it settles.

For a sediment-heavy borewell or tanker supply, many homes use both a spin-down filter on the inlet and a cartridge filter downstream. A plumber familiar with your building’s layout can advise on pressure.

What a Tank Filter Protects

• Pipes and taps: less grit to wear washers and block aerators.
• Geysers and washing machines: less sediment settling inside heating tanks and inlet valves.
• Your drinking water purifier: less sediment arriving at its pre-filter, which then clogs less often.
• The tank itself: less sludge building up between cleanings.

Why It Does Not Make Water Drinkable

A sediment filter removes particles above the size of its mesh or cartridge. Bacteria and viruses are far smaller, and dissolved salts, fluoride, arsenic and nitrate are dissolved, not particles at all. So water after a tank filter can look clear and still be unsafe. Stored water can also pick up microbes in the tank and pipes after the filter.

What the purifier needs to be depends on the source. Borewell water often needs RO, as our guide on whether borewell water is safe to drink explains. Tanker water varies from load to load, so it needs a purifier that can handle the worst load, covered in our guide to the best water purifier for tanker water.

How Often and How to Clean the Tank

A tank filter does not replace cleaning. A sensible routine is to clean overhead and sump tanks at least twice a year, and more often if you rely on borewell or tanker water, after the monsoon, or whenever you see sludge, smell anything odd or find something has got in.

1. Plan the supply. Store enough water for a few hours and switch off the pump.
2. Drain the tank through the outlet or a drain valve, not through the house taps, so sludge does not enter the pipes.
3. Remove the sludge and scrub the walls, floor and lid with a stiff brush. Avoid metal brushes on plastic tanks.
4. Disinfect with a chlorine-based disinfectant made for water tanks, following the product’s dilution and contact-time instructions.
5. Rinse thoroughly and drain the rinse water, then refill and run the taps until any chlorine smell fades.
6. Check the lid and overflow. A tight lid and a meshed overflow keep insects, birds and debris out.

Never enter a sump or large tank alone. Enclosed tanks can hold stale air, and slippery floors cause falls. For underground sumps, a professional tank-cleaning service is the safer choice.

What Boon Does and Does Not Sell

Boon does not sell water tank filters, spin-down filters or whole-house sediment filters. Buy those from a plumbing supplier and have them fitted by a plumber who knows your building.

What Boon makes is the second device in this article: the point-of-use purifier for drinking water. Boon Homie is a wall-mounted RO with a 5-stage UltraOsmosis process, including two 5-micron pre-filters and a membrane rated for input up to 2000 TDS, with in-line LED UV before its 8-litre tank. WaterAI shows input TDS, output TDS and filter health, so you can see when sediment from the tank is wearing the pre-filters. It is ₹21,900 at the time of writing, with free installation by Boon’s own team and a 2-year warranty. If your water is low-TDS municipal supply, RO may be more than you need, and a UV or UF purifier is worth considering.

Frequently Asked Questions

What does a water tank filter do?

A water tank filter catches sediment such as sand, silt and rust before it enters your overhead tank or the pipes that feed your home. That protects taps, geysers, washing machines and your drinking water purifier, and keeps the tank cleaner between cleanings. It does not remove microbes, dissolved salts or chemicals, so it does not make water safe to drink.

Is water from a tank filter safe to drink?

Not on its own. A sediment filter removes particles, but bacteria and viruses are far smaller, and dissolved salts, fluoride, arsenic and nitrate are dissolved rather than particles. Water can also pick up microbes in the tank and pipes after the filter. Use a point-of-use purifier at the kitchen for drinking and cooking water.

Where should a water tank filter be installed?

On the pump’s delivery line into the overhead tank if you want to keep sediment out of the tank, or on the outlet that feeds the house if you mainly want to protect pipes and appliances. Outlet filters run on low gravity pressure, so they must have low resistance. Many sediment-heavy homes use a spin-down filter on the inlet and a cartridge filter downstream.

How often should an overhead water tank be cleaned?

Clean overhead and sump tanks at least twice a year, and more often if you rely on borewell or tanker water, after the monsoon, or whenever you notice sludge, a smell or debris. Drain through the outlet, scrub, disinfect with a product made for water tanks, rinse well and refill. Use a professional service for underground sumps.

What is a spin-down sediment filter?

A spin-down filter sends water in a spiral through a mesh screen inside a clear bowl. Heavier particles such as sand drop to the bottom, and you flush them out through a valve. It suits borewell and tanker water with visible grit and needs no cartridge changes, only regular flushing and rinsing of the mesh. It does not purify water.

Does Boon sell water tank filters?

No. Boon does not sell tank filters, spin-down filters or whole-house sediment filters. Buy those from a plumbing supplier and have a plumber fit them. Boon makes point-of-use drinking water purifiers such as Boon Homie, a wall-mounted RO with UV, which is the device that makes water safe to drink after the tank.