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What are Dry Rainwater Harvesting Systems?

What are Dry Rainwater Harvesting Systems?

Dry rainwater harvesting systems are simpler than wet systems and provide a plentiful source of high-quality drinking water. In this article, we explain how Dry systems work, their advantages and how to ensure you install the system that matches your needs.

How Dry Systems Work

Dry systems work by using gravity to feed rainwater into a storage tank. Rainwater that falls off the roof enters gutters and then downpipes. These downpipes then feed directly into a storage tank.

As the system works with gravity to feed the storage tank, this means that your gutters and piping all need to be above the level that you feed your storage tank.

Advantages of Dry Systems

Dry systems are very simple systems. They work best if you have a simple roof layout and an unobstructed route from the opposite side of the building around to where the storage tank is sited, perhaps a blank wall that is out of sight. This will allow you to keep the piping simple and neat.

As water falls through the system under gravity, there is never any standing water left in the system, like there may be in a wet system. This considerably improves the water quality. Diverters should still be used to separate water possibly contaminated on the roof or guttering, but they can be significantly less complex than those used for wet systems.

For more information on the types of diverters available, how they work and how to size them, take a look at our article, Different Water Diverters in Rainwater Harvesting Systems.

Maintenance is also simpler in dry systems, as the dry nature of the system stops the build-up of contaminants. Having less contaminants in the water also improves the life of your water pumps and appliances too.

The main disadvantage with dry systems is that if you have a complicated roof layout or large building that needs more than two downpipes from your gutters, the piping involved can become messy and complicated. The result can be an ugly tangle of plastic on the outside of your building. In this case, a wet system may be a better choice.

Why Choose a Dry System Setup?

  • If you have an easy route to run piping from one downpipe to another, a dry system is a very simple way to collect rainwater for storage.
  • They can become messy if your building is not simple, but in general, they are easy to plan and maintain.
  • You can be sure of a high-quality of water as there is never any standing water in the system and with the use of some simple diverters, you can build a clean and robust system.