Recycle rainwater: do-it-yourself methods against drought

Discounts on the water bill for those who install at home rain recovery systems. It happens in England and Wales, but one wonders whether, in times of ever more prolonged and frequent droughts, similar incentives for the recycling of rainwater shouldn’t be given in Italy too. Among the Europeans we are by far the ones who use the most water: 220 liters a day per capita, against the 204 of the Portuguese, the 170 of the French, the approximately 130 of the Germans, Spaniards and the British. A negative record due in part to having always been used to an abundance of water. “But also because our country lacks a water resources policy”, he comments Julius Contebiologist, expert in water management and already author of the volume about fifteen years ago Clouds and toilets: how to use water better at home and in the city. “Unfortunately not much has changed since then, while in the rest of Europe water saving and the recovery of gray and rainwater were encouraged. We adopted the same strategy as in Ancient Rome: there is little water to meet the demand growing? Let’s look for a new source and build a new aqueduct”.

The result is there for all to see: very high quality water that travels for hundreds of kilometres, only to be used only minimally (about 10%) for food. The remaining 90% goes for personal hygiene, domestic cleaning, irrigation, industrial uses. “The only progress has been the redesign of the toilets, which has made it possible to save water when you flush the toilet,” explains Conte. “In the past, 12-15 liters were needed, today 6 are enough”. The regulatory gaps are sensational. Like the one that prevents the Municipality of Rome from reusing the water treated by purifiers (93% of the total) to wash the streets or irrigate public parks: in the end they are thrown back into the Tiber. Just as sensational is that in decades of incentives for building renovations the focus has always been on energy efficiency and never on water efficiency.

So it’s good to ask ourselves whether, waiting for politics to become aware of the problem, it’s not the case to go it alone. Starting with the recovery of rainwater. It has been calculated that in Milan a building with a roof of 140 square meters can collect over 120,000 liters of rain a year. Of course, rainfall varies in different areas of the country and may decrease in the future due to climate change. But rain is still an often wasted resource, especially when it is conveyed to the sewers and not to the land.

Systems for collecting rainwater

Here then are multiplied i rainwater harvesting devices, to be installed near the descendants of the gutters. These are barrels (with variable volumes, but which also exceed 200 litres) often made of recycled plastic. A collector is installed on the descending pipe and diverts the water collected from the roof towards the barrel, after having filtered it. A tap in the lower part of the barrel allows you to tap water, to fill buckets or watering cans. Among the models available on the market there are the more spartan ones and those disguised as wooden barrels, terracotta wineskins, marble columns, for a cost that fluctuates around 100 euros. On the other hand, an expense of a few thousand euros must be budgeted for if you want a real 5000 liter tank, to be buried underground and from which the water can then be extracted with an electric pump.

“Rain is great for watering”, says Conte, “even if in our latitudes in order to be independent in the summer you need to have accumulated a lot of it in winter and autumn”. In short, a garden barrel is not enough.

“In Germany, where rainfall is much more frequent, they use rain for household appliances: being free of limescale, it causes far fewer problems”, continues the biologist. But this type of use requires an ad hoc design of the plumbing systems: “In many German buildings, rainwater is collected in underground tanks and then used to feed the condominium washing machines”. The other option to save drinking water would be the use of gray water. “We eliminate them in huge quantities, while after a simple purification treatment, they could be used for watering. But even in this case, small modifications to the existing systems would be needed, so that the gray water does not end up in the sewers but outside the houses where perhaps, in a small pond, some plant varieties provide for their phytodepuration. Today it seems complicated, but it will be the best solution in a future that is increasingly poor in water”.