Rainwater tank packs

A complete rainwater tank pack is not limited to the tank itself: it must also include an inlet filter, a flow restrictor, an overflow, a floating suction, and a pump suited to the intended use, ideally complemented by aeration. The tank volume is calculated based on the roof area, annual rainfall, and your needs. A well-thought-out pack helps you avoid problems with cloudy or odorous water from the very first season.

Collecting rainwater is an increasingly common practice: watering the garden and vegetable patch, outdoor cleaning, and even supplying toilets and washing machines. Tank packs simplify purchasing, but their contents vary widely from one offer to another. Experts in aquatic environments since 1998, we explain what a pack should really contain.

What a tank pack should contain

A successful pack forms a coherent system, in which each element plays a specific role to keep the water clean and easy to use.

Many entry-level packs are limited to the tank and a tap. This is sufficient for a small collector placed under a downpipe, but a tank of several thousand litres, used all year round, benefits from being equipped with all these elements. They are what make the difference between clear water and water that smells like rotten eggs after a few months.

Choosing the tank: above-ground or underground

There are two main families of tanks:

• Above-ground tanks are placed on the ground, against the house or at the back of the garden. Easy to install and inexpensive, they are suitable for small and medium volumes. Place them in the shade and choose opaque ones: light and heat promote algae growth and water degradation. They must be emptied or protected from frost in winter.
• Underground tanks, made of concrete or polyethylene, allow for large volumes without cluttering the garden. The water remains cool and in the dark all year round, which limits its degradation. Their installation requires excavation and often the intervention of a professional.

There are also flexible tanks, interesting for a crawl space or low space, and decorative wall tanks for small areas.

Calculating the volume you need

The ideal volume results from a balance between the water your roof can collect and the water you will consume.

Let's take an example. A roof of 100 m² on the ground, in a region where it rains about 800 mm per year, with a coefficient of 0.85: 100 × 800 × 0.85 = 68,000 litres of recoverable water per year. This does not mean that you need a 68,000-litre tank: rain is renewed throughout the months. The tank must above all cover your needs during dry periods. For watering a medium garden, a few thousand litres are often enough; to also supply the toilets and washing machine, you need to plan for significantly more.

Choosing the pump according to use

The pump is the element that really makes the tank a practical piece of equipment. The choice depends on the use:

• For simple watering, a submersible pump for a rainwater tank, with a float switch, is enough. It starts when needed and stops when the tank is empty.
• For pressurized use (several taps, sprinklers, toilets and washing machine), we choose an automatic pump that starts when a tap is opened and maintains pressure in the network.

In both cases, associate the pump with a floating suction: it draws the clearest water, just below the surface, and avoids drawing up the sediment at the bottom.

The steps to a successful installation

1. Choose the location: in the shade for an above-ground tank, on flat and stable ground capable of supporting the weight of the full tank.
2. Install the collector filter on the downpipe or upstream of the underground tank.
3. Place the flow restrictor at the bottom of the tank and connect the overflow to a suitable outlet: soakaway, rainwater network or infiltration area.
4. Install the pump and the floating suction, then connect the outlet with wall sleeves and watertight valves.
5. Add the aeration: dry air pump, hose and diffuser at the bottom of the tank.
6. Test the whole thing after the first rain: filling, overflow, pump start, absence of leaks.

Tank maintenance

A well-equipped tank requires little work:

• Clean gutters and collector filter in spring and autumn.
• Rinse the pre-filtration foams when they become clogged.
• Check the operation of the pump and aeration each season.
• Drain and remove the sediment at the bottom every few years, if necessary.
• Protect an above-ground tank from frost in winter.

A biological treatment like Aquipond BactoRain can complete the maintenance by helping to break down organic matter at the bottom of the tank. To keep clear water daily, also consult our article on bad odours in a rainwater tank.

The most common mistakes

• A translucent tank in full sun: the water turns green in a few weeks.
• No inlet filter: leaves and moss accumulate at the bottom and ferment.
• A pump that draws from the bottom: it brings up the sediment, clogs itself and blocks the sprinklers.
• An undersized or poorly connected overflow: during a thunderstorm, the water overflows against the foundations.
• An oversized tank for a small roof: it remains half empty and the water stagnates in it for a long time.
• Forgetting winter: a full above-ground tank can deform under the effect of frost, and a pump left outside can freeze.

Putting together your own pack

If your tank is already in place, or if you buy it separately, you can put together your own pack by adding the missing accessories. We offer the elements that make the quality of an installation: pumps for rainwater tank, floating suction, aeration kits, pre-filtration foams, biological treatments, wall sleeves and valves. Start with what has the most impact on water quality: the inlet filter and aeration.

Frequently asked questions

What should a rainwater tank pack contain?

At minimum an opaque tank, an inlet filter, an overflow and a tap or pump. A complete pack adds a flow restrictor, a floating suction and aeration.

What size tank for a house?

It depends on the roof area, local rainfall and use. A few thousand litres are often enough for watering; supplying the toilets and washing machine requires a larger volume.

Above-ground or underground tank: what to choose?

The above-ground tank is simple and economical for small volumes. The underground tank keeps water cooler and is suitable for large volumes, but requires excavation.

What pump for a rainwater tank?

A submersible pump with a float for simple watering, an automatic pressurized pump for several water points or domestic use.

Can accessories be added to an existing tank?

Yes. Filter, floating suction, aeration and pump can be added to most tanks, through the manhole or via wall sleeves.

How to prevent the water in the tank from smelling bad?

Filter the water at the inlet, keep the tank in the dark, oxygenate it with an air pump and a diffuser, and draw the water from the surface.

Also read

• Bad odours in my rainwater tank, what to do?
• Rainwater that smells, should I worry?
• How to take care of the pond after the rains and heavy thunderstorms?