Yesterday, we wanted to test the pipework that we installed (for the rainwater collection off the roof) two years ago and make sure that the position of the ends of the pipe lines (two of them, one coming from the front of the building and the second one running along the back) which terminate just beyond the end of the swimming lane. It was a matter of levels and whether the rain water would flow reasonably easily down these pipe lines and confirm whether we need to readjust anything. We poured in about 120 litres of water (10 buckets) in a downpipe point furthest away and waited to see what happens. We had two right angled bends plugged into the two ends and pointed them down into a large 75litre trug. It took about 5 minutes before any sign of water arrived and only on the front pipeline. Nothing arrived on the back one. we left that to dribble over lunch as it was quite slow.
After lunch, the large trug was full but not overflowing so we only got back about 75 litres of the 120 litres we put in, which means the pipework has very small dips in various sections which needed to be filled up before allowing excess water to flow pass. This will be trapped water for all time, but it is not bad at all, for this amount of water, considering our roof will be collecting 360litres of rainwater for a single millimetre of rain fall!! The only concern is for the pipeline running along the back of the building so we did some more tests by pouring in five more buckets of water in two more downpipe points behind the house, in between the Great Room and Bedroom 2. We did get some water to finally appear at the second pipeline but not much at all, most of the five buckets load went around the long way around the front of the building. This means that we have a small hump (a rise in the level of the pipes) somewhere between this point and the short run to the rain filtration module. The last thing we did yesterday in testing this out, was to carefully pour one bucket into the downpipe point (we label this one “LM” which is next to Bedroom 2 and Bedroom 1 – see map below) and we put two separate empty buckets under each of the two pipelines to find out what apportion of water went which circuit of the pipelines.
In the morning, we discovered that a small amount arrived via the back pipeline but most of it went around the front pipeline circuit and filled up our bucket. The final test was to pour another single bucket in the final downpipe point we got along the back of the house, this time being the “IJ” corner (between Bedroom 1 and Bedroom 2) and see where it went. The result was that all of it arrived in the second bucket under the back pipeline route. We concluded that the hump is most likely in the 7.5metres section that runs along Bedroom 2, the “K” wall. We have earmarked a job request for later on, to dig up the sandy soil and see if we can level out the hump in the pipework, but only if it is possible. It is not the end of the world as the rain water will still be delivered to the rain filtration unit but sometimes more slowly than it ought to be.
Anyway, while those tests were being done, we also got on with the designing of the rain filtration module and one aspect of the system, was the slow draining of the “dirty” water, or the first flush of rainwater off the roof, which we don’t want to keep as it could very well contain chemicals like herbicides and fertilisers, blown on the wind from our local farmlands. But the trick is to make this dirty water drain away so slowly that it would take a week or two to go and it hadn’t been topped up with more rainwater. This suggests that we are getting a dryer spell, like 2 or 3 weeks, especially during the summer and there would be more chance of a higher concentration of chemicals landing on our roof. We don’t want this stuff in our storage tank and being used in our house like flushing the toilets or providing recycled water for showers and washing machines. Hence why we want to “throw-away” this dirty water into our soak-away module instead.
One method is to have a plug of fine sand to control the flow rate and we did some further tests yesterday evening, using a 100mm diameter pipe and putting a 100mm depth of sand in the bottom (the end covered in a geotextile material to hold in the sand) and then pouring a quantity of water and timing how much water drained through in a given amount of time. our first test showed that the water was flowing through at about a rate of 6litres per hour which is rather too fast for our purposes. We would like to slow this down to about 1litre per hour so that our “tank of dirty water (which is currently designed to hold about 240litres) would take about 10 days to drain away completely. Our second test in another drain pipe with a different plug of sand but with a taller column of water to emulate more closely the reality of our filtration module but when we put in the water this time, it didn’t flow hardly at all! Very strange and we wondered if we managed to get silt on the top surface of the sand and effectively blocked it, or perhaps the different sand had much finer grain sizes which also served to block the flow of water too.
We walked away from that, discussed the problem and considering alternatives.
Today, we concluded that it would be far more reliable if we used a small water pump instead and have it controlled by the computer in the house, and pump the water up and into leaky hose pipes running along the back of the swimming lane where there will be a small strip of soil for growing various shrubs and climbers.
This does mean that our design for our filtration module is now much simpler and we can narrow down the width from our original 600mm width to a more practical 400mm wide and extend the whole unit backwards towards the mass wall and the fence line. All the electrical apparatus, sensors and control gear can be held in one place near the back of the module and the water can flow backwards toward the location of the pump.
Tomorrow morning, will see the design fleshed out and finalised, but for the remainder of today, we got on with slicing up the plywood sheets we bought last week into narrow strips, ready to build up edges of the Hip portions of the roof plus also the ridge lines too. This build up is necessary to help support the tile battens when we are doing the fiddly angled edges along the hips (which has an extra “flashing” layer added on top of them) and something similar for the ridge lines (but a little simpler).
So we bought six sheets of 15mm thick plywood which got sliced up into 100mm wide strips (actually, we only needed five of the sheets) to produce 60 strips in total. Then we got out most of the left-over strips of 12mm thick plywood out of the garden shed (these came from the rafter building stage) and sliced them up into 175mm wide strips. These left-over pieces gave us the equivalent of 39 and a bit full length strips (2.44metres long) so we only need a further 53 strips to satisfy our requirement of making 92 strips. We will conclude that task tomorrow, along with making 30 strips of 150mm wide (12mm thick) ones too. All these pieces are being stored in the middle of our house under our gleaming new Skylight!!