Jan 17, 20233 min read

Rainwater harvesting

Since 2020 and the refurbishment of the roof of our barn, we had imagined recovering rainwater 🌦️ from the roofs to water our young trees 🌱 in summer.

The realization of this project came up against a problem: its location; the ideal being in the place of the old sanitary block. So we had to wait until the old block was demolished in January 2022 to free up the space.

In May, we placed an order for 3 tanks of 10,000 litres each to be delivered in the autumn and to start the work. During the summer of 2022, we had an unprecedented dry spell 🌵 with only 21 mm of rainfall in 94 days, confirming our choice to have water reserves built up in winter.

Step 1: take delivery of the tanks, prepare the site (layout of networks and layout) and draw up a list of requirements for ordering pipes and ducts.

Step 2: digging a hole 7.5 m wide by 6.5 m long by 2.3 m high, i.e. 112 m³ of earth, which is a lot! Fortunately, the demolition of the sanitary facilities had left a good-sized hole that we deliberately did not fill in.

Step 3: pour a concrete slab at the bottom of the hole to fix the tanks, the principle being to counteract the Archimedean thrust, which could (under certain conditions) make the tanks rise to the surface when they are empty.

To do this, we built a formwork, added welded mesh to solidify the slab and placed the tank fasteners to be poured into the concrete.

Then, all that was left to do was to empty the router... but the truck got bogged down because of the heavy rain that night! We managed to do it with the help of the delivery man, but we still had to rake a lot 😮‍💨.

We also got 13 tons of sand (with a router truck 🤔) to line the bottom of the trenches and the between tanks.

Step 4: putting the tanks in place, before that we have to pump out the water that has accumulated on the slab with the heavy rain 🌧️ of the last few days.

With the help of a neighbour's backhoe we were able to lower them into the hole and slide them into place without difficulty. Then we secured them to the slab with stainless steel cables.

Step 5: We again hired our favourite mini-excavator to dig the trenches for the networks: gravity (the PVC pipes that will collect the water from the gutters), pressure (the pipes that will carry the pumped water) and electrical (to power the pumps). As the water from the roof of the new reception building will also be collected, the opportunity is taken to add spare pipes to the barn.

After unrolling the ducts, gluing the PVC pipes and laying out the manholes, all that was left to do was to put sand (to protect the networks) and warning netting for safety ⚠️ (when digging, it's better not to cut an electric cable!).

We also connected the overflow of the tanks to the drain field of the old sanitary facilities in order to infiltrate the excess water into the ground.

Finally, we quickly filled in the trenches before the next rainstorm...

Step 6: once the networks were connected, we connected the tanks together with pipes so that the levels inside were balanced, without forgetting to send a caving team 😍 to suck out the small plastic chips before the first filling. Then we finished the connection between the collection manhole and the 3 tanks so that finally the water could fill them 🥳 !

A little later (by the time the tanks were half full), we were able to fill in the space around them with soil and between the tanks with sand. Now we just have to wait for winter and the soil animals 🪱 to do their job so that the land can recover its natural look.

Step 7: Restore all the space around the site, fences, truck ruts, stairs, paths and grassed areas.

Step 8: Finish backfilling the trench and re-connect the electrical connections in the tool shed. We dug and reorganized the sheaths, for that we had to disconnect and reconnect all the cables that arrive in the panel ⚡ ! As we had no more sand to fill the hole, we went to the quarry in Vercheny to get some.

We took the opportunity to hang the tools on the walls and finalize this hut!

To finish, we just have to put the submersible pumps in their place and connect them.

And here we are, we have a nice water reserve for the next summer, which should naturally be rainy, just to prove us wrong 😅