A couple of years ago I posted a piece about my water harvesting setup. I just read it through and realise that for most people it is much more complicated than necessary. I want to describe a relatively simple way to increase water storage, based on part of my system.
Sue’s glasshouse has a footprint of 18.25m2. Our annual rainfall is 1350mm, so the glasshouse roof could potentially collect 18.25 x 1350 = 24,637.5 litres. That’s a lot of water.
There is an integral gutter down both sides of the glasshouse and with the wisdom of hindsight I would have constructed the glasshouse with a slight fall, perhaps 1:500, front to back. For many years the gutter on one side was open both ends and the water ran out into tub trugs at both ends. On the other side it was blocked at the back and at the front ran via a length of pipe into a 230L water barrel a meter or so away from the glasshouse. The barrel had a tap but we usually dunked a watering can in the top. The pipe was a Heath Robinson affair and being at gutter height (1.38m, 41 6”) we walked into it all too frequently.
When I built an extension onto the glasshouse in 2021 I was determined to improve things. The low flying pipe had to go and the storage volume needed to increase as the barrel was quickly emptied in summer.
I put a water barrel at one rear corner of the glasshouse with the flow from the gutters feeding into it. A length of aluminium profile carries the water across the rear end of the house. I kept the lid provided with the barrel and made holes just big enough to feed the water into it. To the tap take off I connected a 20mm LDPE (low density poly-ethylene) pipe which runs along the side of the glasshouse, just below ground, to join the original water barrel located conveniently a few feet from the glasshouse door. Rainfall feeds into one barrel and via the connecting pipe, fills them both. When a can-full is scooped from the front barrel, it is replenished from the back barrel. The water level in the two barrels always remains the same. All I need to do is keep the gutters clean and we get an excellent supply of clean rainwater.
Both barrels have to be at the same level but while the collecting one probably needs to be adjacent to the glasshouse or whatever other water source you have, the second barrel could go anywhere. Furthermore, put a tee into the connecting pipe and you could connect any number of additional barrels and position them wherever is most suitable.
Alternatively you could have multiple collecting barrels feeding into a common pipe and whatever storage you chose. You could for example, have small, slimline water butts on a number of downpipes from your house gutters and feed them into a large storage tank behind the garage which has a submersible pump permanently in it. Once the pipe connections are made the water level will be the same across the system. It made be sensible to have valves in the pipe network so parts can be isolated, or you could have taps to draw water off at any point.
It may be that adjacent to a house you have hard surfaces that make burying pipes impractical. I connect one collecting water butt to my main storage with a hose; both butt and storage have quick click connectors and isolating valves. When the rain stops I put the hose away. It’s much easier than pumping the collected water.
Ldpe pipe is connected with barbed fittings and I would suggest using fittings that have a locking mechanism for the joint. Without them the joints tend to leak or come apart. You will need to heat the pipe to get it onto the fitting, dipping in hot water does the job. It is a simple system to install and not expensive, and the payback in terms of water saving if you’re on a meter, and convenience in having water just where you need it, makes it very worthwhile.