GRPHot Water Tanks

Yes, provided the tank is manufactured and certified to WRAS standards for use with wholesome water. Always check the specification sheet before ordering, as some GRP tanks in the wider range are built for non-potable or industrial applications only. If in doubt, ask us to confirm the WRAS status of a specific model before you buy.

GRP tanks are generally more rigid and better suited to larger capacities or sectional construction, making them a good fit for commercial installations or where a tank needs to be built up on site. Polyethylene tanks tend to be lighter and cheaper for smaller domestic volumes but have less structural strength at scale. GRP's inherent resistance to corrosion and impact also gives it an edge in harsher environments or where longevity is a priority.

This depends on the number of occupants, number of bathrooms and your household's typical hot water demand. As a rough guide, a family of four with a standard system will often need somewhere in the region of 150 to 250 litres, though larger properties or those with power showers may need more. We'd recommend checking your existing cylinder capacity as a starting point, or speaking to a heating engineer if you're changing your system type.

In most sealed (unvented) systems, yes — an expansion vessel is essential to accommodate the increase in water volume as it heats and to prevent excessive pressure building in the tank. Vented systems that feed from a header tank are less dependent on one, but it's still good practice to include appropriate pressure relief. Always follow the tank manufacturer's guidance and current Building Regulations Part G3 for unvented hot water storage.

GRP tanks handle exposure to the elements well thanks to their corrosion resistance, and many are suitable for external or plant room installation. However, hot water storage tanks should always be insulated adequately, and in colder locations, additional frost protection or lagging is worth considering to reduce heat loss and protect associated pipework. Check the specific product listing for guidance on indoor versus outdoor suitability.

GRP tanks are low-maintenance by design, being resistant to rust and corrosion unlike traditional metal cylinders. Routine checks should still include inspecting seals, fittings, insulation and any expansion or pressure relief valves for wear. For unvented systems, an annual service by a competent engineer is a Building Regulations requirement, so factor this into your maintenance schedule regardless of tank material.