Practical tips for buying rainwater collector as sales surge in France

DIY stores say there are now waiting lists for rainwater collectors as people look to overcome drought restrictions

Rainwater tanks can vary considerably in size and materials, depending on your usage and needs, from small garden tanks to larger reservoirs for interior use
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Sales of rainwater collectors are soaring in France as residents face up to the reality of drought restrictions.

Garden centres and DIY shops are reporting growing demand as people look to save drinking water and reduce their bills.

“People would normally use drinking water to water their gardens,” Stéphane Cintract, who is in charge of local life in Beaumont-Saint-Cyr (Vienne, Nouvelle-Aquitaine), told France 3. “But nature gives us water, so we might as well collect it [to use] instead of pumping groundwater.”

Demand is soaring across the country, with one director of a DIY centre in Vienne saying that the waiting list for a tank has quadrupled in length, with delays of up to 15-20 days for a 500-litre tank, and as long as two months for 1,000 litres.

“We’re victims of our own success,” said Benoît Fradeau. “Usually, we sell two vans’ worth of tanks, but now we’re going to have six or seven vans, so there is really a run on water tanks.”

Corinne Barbet, manager of a DIY store in Jura (Bourgogne-Franche-Comté) that is seeing rising demand, said: “Given the drought that we had last year, people are naturally wanting to collect their rainwater, so they can at least water their garden.”

Tips for buying your own rainwater collector

1. Calculate your savings and check the size of tank you need

Figures from the statistics bureau Insee show that the average 2.5-person household in France consumes around 329 litres of water per day. Of this, 7% goes towards cooking, and 6% towards watering the garden and washing cars.

Tanks typically range in size from 200 to 5,000 litres, and it is possible to collect up to 600 litres of water per year, per metre square of roof.

2. Consider the type of tank you would prefer

Some tanks are underground, while others are above ground. Both are typically filled via a gutter pipe.

Most are made of concrete or polyethylene and the best kind will depend on how you intend to install it, and where.

Concrete tanks (along with the relevant filtration systems) can be used for collecting water that will eventually be drunk, whereas plastic containers tend to be used for outdoor tasks.

The cost varies from around €30 for a small tank up to several hundred euros for the largest. Installing a concrete, underground tank for inside use with connections to the wider network can run to several thousand euros, depending on the scope of the job.

It makes sense to check the size of your roof, and do a rough calculation to see how much water you could collect per year, so you can buy the best-value, best-sized tank for your needs.

3. Check if your area is offering support or a scheme for water tanks

Some towns are offering financial support to residents who order a collector - including Beaumont-Saint-Cyr, Migné-Auxances (Vienne, Nouvelle-Aquitaine), and the greater Niort area (Deux-Sèvres, Nouvelle-Aquitaine).

Using a similar scheme near you could save you considerable money.

In Niort, authorities are offering a loan of up to 80% pre-tax, up to a limit of €180, for tanks of 300 litres or more. In Migné-Auxances, residents have joined together to make a group purchase.

In Beaumont-Saint-Cyr, the town’s scheme enabled the residents to work together to buy 104 tanks of 1,000 litres each, enabling each resident to save up to €50.

Around 100 people in the town have signed up.

One resident, Eric Marie, told France 3: “At €144 per tank, it’s not far off the €130 in the shop, and compared to the €160 in some shops, it’s an advantage.”

Homeowners in Ile-de-France, the region around Paris, can even benefit from government aid of up to €20,000 to help build a rainwater collection system in a scheme intended to save money and help the environment.

Read more: French region offers €20,000 for rain collectors as popularity surges

4. Be aware of the water usage rules

The rules also state that collected rainwater must only come from a roof run-off, from a roof that is not otherwise accessible (except via ladders when needed, for maintenance and upkeep.

No anti-freeze materials can be added to the tank at any time.

Rainwater can only be used for domestic tasks, and cannot be used for drinking water unless you have installed a legally-compliant filtering and cleaning system (which includes testing the water’s pH). Filtration systems tend to use microfiltration, ultrafiltration, or reverse osmosis.

Indoors, it can legally be used for three tasks:

  • Filling toilet flush tanks
  • Washing floors
  • Washing clothes, as long as you use a suitable water treatment system

If you use the water indoors, and the used water is then collected by the mains water system, you must declare it with une déclaration d'usage, which you can do via the water cleaning department of your local Mairie.

Outdoors, you can use it as you wish on your own property, including cleaning vehicles and watering plants.

5. Consider safety and covering measures

When installing your tank, be sure to put it close to a gutter on a flat and stable surface, and protect the eventual water from debris. This includes:

  • Covering the tank with a mesh or grid
  • Cover the tank with a mosquito net to avoid insects from entering
  • Installing a filter-decanter that separates the water from impurities
  • Cover the tank to avoid the formation of algae or other microorganism growth

Your tank will also need to be cleaned twice a year - for example, before the winter. You can do this by emptying the water inside it, and cleaning it with a jet washer.

During the coldest months, to avoid the water from freezing and potentially damaging the system, it is advised to empty the tank and let it remain empty for the duration of a cold snap.

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