Rainwater makes Cox’s new wash-down system a first

Liana being power washed at Cox's

An innovative, eco-friendly boat wash-down system has recently been designed, built and installed by the team at Cox’s Boatyard, with help from an £8,900 grant from the Broads Authority’s Sustainable Development Fund.

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Eric Bishop, the boatyard manager, and his team, were keen to ensure that the run-off water from around 200 boats they wash down each year has no detrimental impact on the environment.


They have devised a closed-loop system that not only harvests and uses rainwater from the boatyard’s roof, but also passes all used water through a set of purifying filters. The cleaned water can then either be used again, or discharged safely into the Broads.


Closed-loop systems have been used on a limited basis elsewhere in the country before, but this is believed to be the first time that harvested rainwater has been incorporated into the design.


Pressure washing is a vital method of keeping boat hulls in a good state of repair, by removing old anti-fouling coating, paint, weed, algae and invasive species, especially in the autumn before boats are over-wintered. Unfortunately, the run-off water from this type of high-pressure cleaning can contain antifouling residues, paint fragments and other chemicals, all of which could work their way into rivers and waterways. The new system at Cox’s means that not only pure, clean water is discharged, but also that it can be recycled and re-used, along with harvested rainwater, many times on an endless loop.


Eric Bishop says: “We are keen to implement any systems that help preserve the future of the Broads for both wildlife and for boat owners. This £18,000 system is part of a major eight-phased development plan for the boatyard. It took only five weeks to install, and it is already doing a great job. We are looking forward to further improving our services to boat owners in the future.’


The system collects rainwater and stores it in a 6250-litre tank, from where it is piped to an area used for pressure washing. Boats that need cleaning are suspended from the yard’s crane, which can lift up to 9.5 tons, and positioned above a large concrete pad, with angled sides that funnel the run-off water into a small, central drain and tank. Here water-borne particles and debris, as well as invasive species such as the ‘killer shrimp’ (Dikerogammarus villosus) settle out from the main body of collected water and sink to the bottom. Killer shrimps are aggressive predators that prey on native shrimps and young fish, and they have recently been found in Barton Broad, so any system that helps to prevent their spread has great environmental importance.


Once the larger debris is removed, an automatic pump sends the waste water via a pipe to a 4000-litre storage tank, which is situated alongside the rainwater tank. When this second tank is two-thirds full, the water is pumped at a rate of 85 litres per minute though two special filters, which are reusable and washable, to remove any remaining pollutants.


The pure, filtered water can then either be re-used, or returned to the river, meaning that even in a drought when there is little or no rain water there is always an ample supply of water available for washing down the boats. Neither does cold weather cause any problems, as all the pipes and cables have special heat cables fitted to them to stop them freezing.

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