25Litres - 100 Litres

Tanks in this size range are popular as header tanks, small break tanks, chemical dosing vessels, or top-up reservoirs for pumps and irrigation systems. They're also widely used in caravans, boats, plant rooms and small-scale rainwater harvesting setups where space is tight. Because they're compact, they suit applications needing a buffer volume rather than bulk storage.

Some are, but not all — check the product listing for WRAS approval before using a tank for potable water. WRAS-approved tanks are made from materials safe for wholesome water contact and are commonly used as header or break tanks in domestic plumbing systems. Non-WRAS tanks should be reserved for non-potable uses such as chemical storage or greywater.

Most tanks at this size are moulded in polyethylene (MDPE or HDPE), which is lightweight, corrosion-resistant and easy to fit with standard tank connectors. Polyethylene is also naturally UV-stabilised in many outdoor-rated products, though it's worth checking if the tank will sit in direct sunlight long-term. GRP is less common at this scale but does appear in some chemical-resistant or bespoke dosing tanks.

Many small tanks are supplied plain, without pre-fitted bosses or connectors, so you'll need to drill and fit your own tank connectors, ball valves or bulkhead fittings to suit your pipework. Some listings do include a lid and basic fittings — always check the specific product description rather than assuming. If you're dosing chemicals, make sure any fittings you add are compatible with the substance stored.

Even at 25-100 litres, a full tank is heavier than it looks — water alone adds a kilogram per litre, before the tank and any fittings. They should sit on a flat, level, solid surface capable of taking the full loaded weight, and shouldn't be left unsupported on uneven ground or shelving not rated for the load. For wall-mounted or bracketed installations, confirm the bracket is rated for the tank's full weight when full.