Setting Up a New Rainwater Tank? Find Out What You Need

Collecting rainwater is an economical and ecological way to obtain quality utility water. For all new buildings, a rainwater tank is even mandated by law. If this obligation applies to you or you are intrigued by the benefits of using rainwater, find out what you need for its collection.

Benefits of Using Rainwater in the Household

Collecting rainwater is advantageous mainly for environmental protection and financial savings.

1. Ecology: Drought is becoming an increasingly common problem in the Czech Republic. Most of the Czech Republic suffers from water shortages in the summer. Climate change has caused a lack of rainfall and more frequent torrential rains, but dry soil cannot effectively absorb the water from these downpours. Many people therefore water their gardens with tap water, which is full of disinfectants and harmful to plants and the entire ecosystem. By collecting rainwater, you can store the entire volume of rainfall and gradually water your garden during dry periods.
2. Financial Savings: You can collect rainwater on your property completely free and without restrictions. If you have a roof with an area of 100 m², you can collect up to 6 cubic meters of rainwater per month and save up to 10,000 CZK annually. The initial investment in a rainwater collection and filtration system can be partially covered by government subsidies. From the Rainwater Subsidy Program, you can receive up to 50% of eligible costs.

What the Law Says About Rainwater Collection

Since 2021, the law requires the installation of rainwater tanks for all new buildings. Although this obligation is not legally mandated for older buildings, more and more homeowners are adopting this solution.

Planning to pipe rainwater into your home? Then remember that connecting rainwater and tap water systems is legally prohibited, as it could lead to contamination of the drinking water source. The pipes must be completely separate, or a pipe separator must be installed.

Uses of Rainwater

Properly treated and filtered rainwater has a wide range of uses in homes and gardens. It can be used for:

• watering,
• flushing toilets,
• washing cars,
• cleaning and laundry.

However, it is always necessary to purchase an appropriate filtration system based on the planned use of the rainwater.

For watering, rainwater is much more suitable than tap water

What You Will Need for Rainwater Collection

When planning a system for rainwater collection, consider several aspects:

• the roof area and average rainfall volume in your area,
• the purpose of using the rainwater,
• the expected volume of rainwater consumption.

Based on this information, an experienced designer will propose a system consisting mainly of a tank, pump, and filtration device. These components are then connected to the gutter, and possibly also to piping.

Rainwater Storage Tank

Rainwater tanks vary in volume, manufacturing material, and location – they can be aboveground or underground. Underground rainwater tanks are generally more advantageous as they prevent temperature fluctuations, which inhibits the growth of microorganisms. Therefore, rainwater has a shorter shelf life in aboveground tanks. Additionally, an underground tank will not obstruct your garden. However, the installation of an underground rainwater tank must be carried out professionally.

The tank volume should correspond to the roof area, with barrels of approximately 4 cubic meters suitable for a 100 m² roof. The most common manufacturing material is durable plastic, which is easy to handle and maintain, but you may also encounter concrete and fiberglass rainwater tanks.

NOTE: So-called retention tanks are only used to slow down the outflow of rainwater into the sewer system, thus protecting it during torrential rains. If you want to retain and use rainwater, you need a storage tank.

Pump

Submersible rainwater pumps should be chosen to handle water with mechanical impurities. Note that submersible well pumps are intended for pumping only clean water without impurities. A rainwater tank pump should have dry-run protection, which is most commonly provided by a float. Choose the appropriate pump head height based on the volume of water pumped and the distance to the point of use, and the power based on the required flow rate.

For a simple aboveground rainwater barrel intended only for watering, attaching a tap to the barrel may suffice.

Filtration and Treatment of Rainwater

Choose the method of rainwater purification based on its intended use:

• For water intended only for watering, place a filter basket on the downpipe before the tank.
• For water intended for toilet flushing, add a mechanical water filter before the pump in the tank, and ideally also a carbon filter to remove odours, organic substances, and dissolved chemicals. For rainwater filtration needs, the Triplex filter from Honeywell is suitable, consisting of a pre-filter, a fine mechanical impurity filter, and a carbon filter.
• If you decide to use rainwater for cleaning or laundry, choose a greywater treatment plant.

Honeywell Triplex rainwater filter

Maintenance of the Rainwater Collection System

All components of the rainwater collector require maintenance. Regularly empty the rainwater filter basket located in the geiger and rinse the mechanical filter screen. Carbon filters require regular replacement of the filter cartridge, with the replacement interval determined by the manufacturer.

The tank should be cleaned from the inside from time to time, as algae and other microorganisms that degrade the stored water can multiply in rainwater. For the pump, it is only necessary to ensure that it does not become clogged with particles larger than those allowed by the manufacturer. If the pump has dry-run protection, or a float, you need not worry about malfunctions.

If you choose a suitable rainwater collection system and maintain it properly, you will gain an excellent source of quality utility water. Your garden and wallet will thank you.

Choose a suitable rainwater filter