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Ablution Plant - Hotel Chain Case Study

The problem presented itself in the shape of a refurbishment of a major hotel in London, the hotel wanted to insure it catered for an international clientele and respected any requirements based on cultural needs.

The problem presented to Arrow Valves was to come up with a solution that provided safe hot water between 36° and 41°C for a bidet shower hose. To clarify the situation, a bidet hose would be risk assessed at Fluid Category 5 and would thus require an air gap in order to protect the water supply from possible contamination. To follow the Water Regulations correctly, point of use protection is required therefore each outlet requiring individual protection.

In order to provide Fluid Category 5 protection this is normally achieved by using a Break Tank with a weir overflow. The problem with using a Break Tank is we lose all water pressure and have to use a pump in order to boost the pressure to a usable level. Additional problems with the above scenario are that we need hot water in order to blend it down to the correct temperature. If we fed the Break Tank with hot water it would get cold when the unit was not in use and become a breeding ground for bacteria and furthermore the tank would have to be emptied of cold water before we have a usable supply of hot water.

Our initial thoughts to solve this problem was to have a conventional cold water Break Tank, thus providing the required air gap, a pump to increase the pressure and then a water heater and finally a TMV3 (Thermostatic Mixing Valve) to regulate the temperature of the water to a safe level. We considered an instantaneous heater, but these require a 12 kW electrical supply, and when adding multiple units could overload the electrical supply to the building should all be on at once. A conventional 10 litre (later to become 5 litres) water heater running at 1.9 kW was used providing stored water at 62° C (above bacterial development).

Of course this all had to be contained in as small a package as possible in order to fit within the water risers and be quiet at 45 decibels so it would not intrude into the rooms. The components were housed in a 1000 mm tall cabinet 400 mm wide and 210 mm deep. It has 25 mm of sound deadening foam around the moving parts. The unit has 1 electrical connection, 1 water inlet and 1 water outlet, it’s fully automatic and can be installed without the need for factory commissioning. The success of the unit resulted in 152 installed in the hotel, and the product to be included in the Arrow Valves catalogue and has continued to be specified and installed in many prestigious locations throughout the UK.