What is a sand filter?
This is a water-soluble, plastic filter that you fill with sand to stop pollution and pollution-related problems from happening.
In some parts of the world, it’s also used for filtering the water supply.
But sand filters can be very expensive, costing up to £1,500 ($1,800) for a set of pumps that can filter up to 300 litres per hour, according to the Environmental Protection Agency (EPA).
A water filter costs about £1 ($1.20) in some parts.
But it’s not just water that can be filtered with a sand-filter pump.
It can also be used for cleaning.
If you have a home with a leaky roof, sand filters could help stop it leaking.
Image caption The filter will only take water through the pipes to the filter