Nautilus - Non Return Valves Brochure

Non-return valves are installed to the inside of the manhole. These are fully automatic and they stop backflow of sewage into a property. As surcharge occurs, the float rises and closes the valve. This isolates the property from the sewer. During surcharge inside the sewer, the valve is forced shut preventing backflow into the property. Significantly the valve still allows normal flow out from the property. When the surcharge has passed, the valve automatically opens.