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McMullin & Co
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Improved rainwater balance

In 1994 we began to receive lots of requests for information about methods for collecting rainwater. In response to this demand, we soon thereafter published a design for a 'rainwater balance'.

In the meantime, the number of people interested in collecting and reusing rainwater has increased dramatically. You see more and more rainwater barrels. People who are really committed have underground water-tanks and those who are really fortunate have water cellars at their disposal. There's one problem: after long periods of dry weather, how can you prevent the first surge of rainwater that flows into your collection tank from being polluted by dirt and other matter (especially bird excrement)? For this, we developed a rainwater balance that didn't have many faults, except that it was fairly complicated and couldn't handle much water. So, can it be done more simply and with greater capacity? Yes, but you must use professional piping.

First, a tip, this task is unnecessary if you have (1) a roof on which birds rarely land or leaves fall, and (2) if you do not want or need to collect high quality rainwater, because you'll only be using the rainwater for watering the garden. Prior to beginning, ensure that the rainwater is filtered before it enters the rainwater pipe, by using, for example, a layer of finely ground nylon netting, which is spread over the roof gutter's discharge point or over the drainage point. It's also wise to do some extra cleaning in the autumn; but this will require climbing on the roof.



This time we are going to use material available at professional supply stores: a piece of pvc-piping with a diameter of 125, 160 or 200 mm (usually 80 or 100 mm). The thick piping on the underside has a sealing cap glued on to it and just above this we attach a faucet (for example, a plastic barrel faucet), which allows the first flow of water to wash away during the first rain shower. The pipe is given a pivot near the bottom by simply drilling two shallow, slightly eccentrically placed holes in the rim of the sealing cap, into which two adjustable bolts measuring 8 -10 mm fit, and which can support the piping with two supports. Ensure that one is attached to the wall of the house or is located just under the thick pipe or that a piece of chain is used on the pipe to provide the required space for the channel.

In its empty, neutral position, the opening of the thick pipe is under the rainwater pipe. If it turns, after collecting a certain amount of dirty water (in an average sized home with a semi-sloping roof, you can expect to collect 20-30 liters of rainwater), the attached rainwater pipe with a funnel opening shifts under the drainpipe. This ensures that, via a flexible hose that drains the water, there is a proper transport of clean(er) rainwater. The stiffer the hose, the longer it will be able to properly bend.

If the pipe does not shift position at the desired moment, you'll have to experiment until it works properly, by attaching weights to the pipe.

The tap is there to be used during extremely dry conditions, allowing you to give water to the thirstiest plants.