Catch the rain

With the addition of guttering to the roofs of the buildings we’re renovating, it’s always been the intention to catch and store the rainwater runoff. It’s at this time of year, when the land is parched and the stream down to its bare minimum, that a few thousand litres can make all the difference. The east side of the quinta furthest from the stream suffers the most. Here it’s so dry it’s been pointless trying to establish new plantings or even dream of growing annuals without installing some sort of irrigation to support them. Long-term, the aim is to grow ground cover plants and shrubs that, over time, will increase the moisture holding capacity of the soil by adding organic material to it, and shading the soil from the harshest effects of the sun, but until we get to that point – and even when we do – water in the summer will be important.

While less than ideal from several perspectives, the quickest and cheapest solution to the water storage problem has been to purchase second-hand 1,000-litre plastic IBC tanks. By specifying non-toxic original contents, it’s possible to be reasonably confident you’re not going to compromise the health of your land with toxic residues, though ‘non-toxic’ can include some less than pleasant liquids. A supplier who jet-washes his tanks before selling them is consequently an advantage too. If you can obtain food grade tanks (moulded with a wineglass and fork symbol), better still.

So this is what we did. Amazingly, Lester managed to shoe-horn 6 of them into his van. They went in, but then they wouldn’t come out again. While the crowbar was tempting, we finally managed to extricate them by removing the cradle base of the one that was stuck.

For the primary storage area right next to the wee house, we cut into the bank running between the ground and first floor levels and levelled a site large enough to take 4 tanks.

The cleared site for rainwater storage tanks. The 110mm drain pipe sticking out over the site carries the rainwater runoff from the north side of the roof and the rear section of the south which runs under the paving of the outside kitchen

First IBC tank in position

All 4 tanks in position, levelled, and connected to each other via a 40mm pipe running along the bottom

Supply pipework connected. The waste pipes exiting the two nearest tanks are breather pipes. The main volume of water enters the third tank via the 110mm pipe. The front part of the south side of the roof plus the toilet roof drain into the fourth tank

First flush filter on the main drain. This is just a capped downpipe, but allows any dust and debris washed off the roof to fall into this rather than going straight into the tank. The cap is simply unscrewed for cleaning

A similar first flush filter takes the water from the front south side of the roof and from the toilet roof

There are two outlet lines – the main outlet (left) is to a stand pipe on the terrace below with the potential to install drip line irrigation for the raised beds we’ve made there. The overflow outlet (right) is presently just an overflow, but in time could be linked to another tank on a lower terrace … and another … and another …

The downpipe from the front south side of the roof travels across the front of the house to join the toilet roof gutter. Not the prettiest thing, but there will be a wooden trellis attached to the building here and foliage will cover the pipes

The tanks have been covered with thick black plastic to exclude all light, so there should be no algal growth in the water. The plastic is covered with shade netting to prolong its life in the strong Portuguese sun, which in turn is covered by a trellis. A perennial climber will eventually cover the trellis to provide further shading and insulation

The upper surface of the tanks has been covered with the Fondaline membrane we’ve used on both the turf roofs we’ve made, and then a covering of straw and topsoil

Conveniently, just a few days after we completed this, it rained. Somewhere between 12-15mm at a guess – and the tanks collected around 500 litres. 12.5% of their capacity in one night. I think I’m going to have to install a lot more tanks.