Rainwater harvesting is an incredibly efficient process. It's been common practice in Australia since colonial times. It's not only part of our history and culture, but it's also actively encouraged today.
That being said, have you thought about the best way to plumb your rainwater harvesting?
There are 2 main types of plumbing for rainwater harvesting:
- Wet rain harvesting system
- Dry rain harvesting system
In this blog post, we will discuss the dry system alone in depth.
What is a Dry System and How Does It Work?
A dry system is a plumbing configuration for rain harvesting that’s more straightforward compared to the wet system.
It’s straightforward because unlike in wet systems where pipes go underground or are on the ground, dry systems involve pipes that run from your roof directly to your tank. That is, through the force of gravity, rainwater falls from your roof through your gutters, goes down to your downpipes and then into your water tank.
Why Is It Called a "Dry" Rain Harvesting System?
It’s called a dry system because your pipes will easily drain water once the rain stops; meaning your pipes will eventually dry (no remaining water left inside your pipes thanks to the force of gravity).
In contrast, a wet rain harvesting system could have remaining water inside the pipes as piping is either buried horizontally underground / runs parallel to the ground. This pooled water could be removed using a diverter.
Although the dry system is a more straightforward configuration, it does have its drawbacks.
Here are the specific reasons in which you might find the dry system more superior (or inferior) to its wet system counterpart:
Dry System Advantages
1. Easy installation
2. Simple maintenance
Employing a dry system is often easily accomplished. It’s cost effective and fast compared to what’s involved in a wet system.
Here’s a summary of the benefits of an easy installation:
- Cheaper (requires less materials like joint fittings, pipes and diverters)
- Quick (no pipes need to be buried / no digging necessary like in wet systems)
As mentioned earlier, a dry system is called dry because there is no standing water left in the pipes. During rainy days, water is constantly flowing directly to your storage tank at an angle. This eliminates the occurrence of stagnant water that could become breeding ground for bacteria, mosquitoes and other insects.
Hence, dry systems have lower contaminant counts; plus there is no need for an in-ground first flush water diverter to drain pooled water out of the piping.
Easy detection of leaks
Because the piping for dry systems are located above ground where they are easily visible, any damage or leaks in the pipework can be easily detected by you. This makes dry systems much easier to clean, repair, and maintain over longer periods of time in comparison to wet systems.
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Dry System Disadvantages
1. Aesthetics may be less than ideal
2. Lesser adaptability
Less Than Ideal Aesthetics
If your roof structure is such that you need multiple downpipes running from your roof gutters to your water tank, then the pipe work involved could look messy in a dry system. In this case, a wet system may be considered.
Dry systems require you to have your water tank placed near your main catchment area (roof). This greatly limits the number of options you could have in terms of water tank location.
So, in what scenarios is it ideal or possible to choose a dry rain harvesting system?
When to Use Dry Rain Harvesting
- You have a clear spot for your water tank that is situated near your roof
- There are no obstructions from your roof (and gutter/pipes) to your tank that could complicate access and installation
- There are no multiple catchment areas or too many downpipes involved
Management of a Dry System
We’ve mentioned earlier that wet systems contain more contaminants than dry systems. While this is true for the former when underground pipes are not incorporated with diverters, the reality is that contaminants don’t just come from stagnant water trapped in pipes.
Pollutants could also come directly from your roof, run through your gutters and pipes and find their way into your water tank. In poor conditions, this scenario could just as easily compromise your water storage as standing water that becomes stagnant in wet systems would.
So how do you manage a dry system?
View our blog post below on what components you need to ensure clean, quality stored water:
Every Must-Have Component for Rainwater Harvesting You Should Be Familiar With (Checklist for Beginners)
If the idea of a dry system is still a little confusing to you, it's probably because you need to contrast it against its opposite. Explore dry system's counterpart in this article below:
Needless to say, the right rainwater harvesting design can be an incredibly efficient upgrade for your house or shed on your property.
But consider this before choosing which tank to buy or before you even wonder about water tanks cost:
Survey your property to see which possibilities or limitations present themselves. This way you can make better plans.
Note that your water storage tank of choice could also impact your final plumbing configuration. For instance, poly water tanks, which are more lightweight and adaptable, could easily suit any plumbing, be it the wet system or dry system.
In contrast, if your water storage tank of choice is not as easily adaptable, then you may need to adapt to it instead, which limits your options.
Finding a water tank that would make way for your needs instead of the other way around is a huge plus indeed.
For a list of pros and cons of the different types of water tank material, explore our blog post here:
Key Differences You Need to Know About Water Tanks
Other related topic:
Two Ways to Link Multiple Water Tanks Together to Maximise Rainwater Harvesting Potential
Editor's Note: This post was originally published on September 20, 2018 and has been revamped and updated for the purpose of accuracy and comprehensiveness.