Water & Irrigation — Water Tanks

A reservoir does more than store water. It lets you mix a whole watering in one go, so every plant gets the same EC and pH, and it lets tap water come up to room temperature before it goes into the pot. The choice here is about two things: how many litres, and whether the tank is allowed to stay standing.

Collapsible or rigid

The AutoPot FlexiTank runs from 25 to 750 litres and folds down to a parcel when empty, with sealed seams. AquaKing's collapsible water tanks do the same at 100, 160, 250 and 380 litres, and the dimensions come with them: the 100 litre is 40 cm across and 80 tall at 1.85 kg, the 380 litre 70 by 100 cm at 3.77 kg and packed no larger than 99 x 14 x 14 cm. That makes them the choice for a tent that is temporary. Rigid are the AutoPot 47 litre tank with lid, the 50 litre round barrel and the Garland barrel, which has a foam cushion on the lid so you can sit on it while you work.

Height is functional

On a system that runs by gravity, the height of your tank decides whether water arrives at all. That is why the stand for the 47 litre tank is not an add-on: it raises the tank by 31 cm so the pressure in the system holds up. If you raise a tank yourself, do it on something that carries the filled weight. Which systems this applies to is under Watering Systems.

Full, it stays where you put it

Water weighs a kilo a litre, so a 250 litre tank is a quarter of a tonne once filled and is not going to be moved. Decide the spot before you fill it, and consider what the floor carries and where a leak would run. A lid belongs on it: open water catches light and grows algae, and algae block your drippers later.

Jerrycans and temperature

For 5 and 10 litre jerrycans with a 51 mm opening there is a W51 tap and an opener for caps that have seized. If your water drops too far in winter, the Barrel Heaters hold the supply at temperature; they have a plastic sheath and can go in a collapsible tank too.

Frequently asked questions

How large should my tank be?
At least one full watering, with margin. Too tight means mixing again halfway, and then the second half of your plants gets a different solution from the first.

Can I leave mixed nutrient standing?
Only so long. The pH drifts after mixing and quality falls off in standing water. Mix what you will use within a few days, and circulate it if it has to stand longer.

Is a collapsible tank sturdy enough?
For indoor use, yes; the seams are sealed and the larger sizes are meant to stand full. What you give up is shifting one while it is half full, because the fabric gives.