SITE PREPARATION


with the manufacturers specification. TOO MUCH RAIN


The advantage of collecting rainwater is that it is a relatively simple process and it also has a further benefit regarding Sustainable Urban Drainage (SuDS). During heavy rainstorms water is collected within the tank first, preenting localised ooding. Emerging systems allow a volume of the tank to be used for non-potable applications, but are designed with etra capacity specifically for when there is ecess rain. This etra olume is calculated specific to the site and meets the criteria for severe rain events. Water is released back into the storm drain or soakaway at a controlled rate so reducing the risk of downstream ooding. This can be as low as . litres per second per plot, and so will not oerwhelm the network. It is the overwhelming drainage system that needs to be addressed which is how harvesting rainwater as a SuDS solution would be highly beneficial. Returning water to the storm drain at a controlled rate is an efficient way to collect for reprocessing which may become more important with increased demand. The extra capacity is calculated based on all ‘worst case’ scenarios and any other criteria that planning requires by Micro Drainage.


INSTALLATION A groundworker is required to site the tank under the manufacturer’s instructions. Some tanks are ‘shallow dig’ so only reuire a depth of  - . m making it easy to install in areas where there is a relatively high water table and ease of calculation of levels. There must be a ‘fall’ from the downpipe so the rainwater ows towards the haresting tank. t is ery important that the piping from the roof to the tank is ‘closed’ and there are no open gulleys.


A plumber will then install the pipework to the appliances and connect both the rainwater and mains supply, and an electrician will be required to connect the pump and sensors to actiate the ow of water. Modern systems are designed to make installation relatively simple and therefore should not add significant cost to a build project. Complete systems with mains backup cost in the region of - e T. This cost can be offset with the assistance of a planning application for water usage and drainage strategy. A combined system can be an economic way of achieving a SuDS plan where discharge from site can be actively calculated.


n conclusion, rainwater haresting comes at a small material cost for long term sustainability and as a first line defence against ooding.


Jae Lester is director at RainWater Harvesting 34 www.sbhonline.co.uk nov/dec 2022


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