Collecting rainwater is a smart and sustainable way to manage your household water use, but keeping that water clean from the roof to the tap depends on the setup. Most of the work happens before a filter is ever involved.
This guide covers two stages and the accessories that make each one work: cleaning the water before it enters the tank, and drawing the cleanest water back out of it. For the wider case for collecting it in the first place, see why rain harvesting matters.
Stage 1: Clean the Water Before It Enters the Tank
Stopping debris at the source significantly improves the quality of the water entering your tank, and it reduces the work everything downstream has to do. Debris that gets into the tank settles on the floor, so material kept out at the downpipe is material you never have to flush out later. Two accessories do this job, and they deal with different sizes of problem. The Leaf Eater handles what you can see. The First Flush Diverter handles what you cannot. Used together they cover the range from leaves and branches down to dust.
Leaf Eater
The first line of defence. The Leaf Eater is installed on your downpipe system to catch larger debris like leaves and small branches before they reach your tank. It works at the point where that material is easiest to deal with, in the downpipe rather than in the tank, which is the difference between clearing a screen and cleaning out a tank floor. How often it needs attention depends on your roof: a catchment under trees will load it up far faster than one in the open.
- Purpose: Filters out coarse debris
- Placement: Inline on downpipes
- Maintenance: Check regularly to remove any leaf build-up from the screen
First Flush Diverter
Even clean-looking roofs accumulate dust, dirt and other fine pollutants between rains. The First Flush Diverter captures and discards the first portion of runoff, preventing those contaminants from entering your tank. The longer the dry spell before it rains, the more there is for it to catch.
- Purpose: Removes fine sediment and dust from roof runoff
-
Options:
- 90mm Kit: Suited for 90mm downpipes. No chamber included, so you build your own to the capacity you want from 90mm pipe
- 120 Litre Kit: Includes a 300mm diameter x 1.2m chamber and accommodates up to 100mm downpipe
- Maintenance: Must be emptied manually after each rain event
Using both of these accessories together helps ensure the water entering your tank is as clean as possible from the outset. Both are on our rain harvesting accessories page.
Stage 2: Draw the Cleanest Water From Your Tank
No system keeps everything out, and debris that does enter the tank settles at the bottom. That leaves the tank layered: sludge and contaminants on the floor, and the cleanest water near the top, about 100 to 150mm below the surface. The risk is drawing from the bottom, where that sediment sits. Two accessories deal with this from opposite ends. The Tank Vac works on what has settled on the floor, removing it rather than letting it build up. The Floating Outtake works at the other end, making sure the water leaving the tank comes from the clean layer near the surface. They solve different halves of the same problem, which is why they pair well.
Tank Vac
Instead of letting clean water overflow, the Tank Vac system flushes out dirty water from the base of the tank whenever it overflows. It uses gravity and water pressure to siphon off debris that has collected on the floor of the tank. The useful part is that it runs on an event that was going to happen anyway. Every time the tank fills to overflowing, the tank cleans itself a little, with nothing for you to switch on and nothing to remember.
- Purpose: Flushes debris from the tank floor during overflow events
- Operation: Automatic, activates when the tank overflows
- Maintenance: Low. Simply check that the siphon holes are not blocked and that the system is overflowing correctly when full
Floating Outtake
The cleanest water in your tank is just below the surface, and the Floating Outtake makes sure that is the water you use. No matter the water level, it floats and draws from that ideal height. That is what separates it from a fixed outlet, which can only sit at one height and so can only be right at one water level. As the tank fills and empties across the season, the Floating Outtake keeps tracking the clean layer.
- Purpose: Draws water from the cleanest layer
- Operation: Passive, adjusts with water level
- Maintenance: Low. Occasionally check the mesh intake for blockages
What's the Best Setup?
Each of these components offers benefits on its own, but combining all four, the Leaf Eater, First Flush Diverter, Tank Vac and Floating Outtake, delivers the best results for water clarity and tank hygiene. Each one covers a gap the others leave: two keep material out of the tank, and two manage what gets in regardless.
If you are looking for the most effective and low-maintenance combination, the Tank Vac and Floating Outtake together offer the greatest impact. They clean your tank and ensure the cleanest water reaches your home, all with minimal upkeep. Less material sitting on the floor also means less to deal with when it is time to clean the tank out.
Want Help Choosing the Right Setup?
The right combination depends on your roof, your tank and how much maintenance you are willing to do. A catchment under trees puts more load on a Leaf Eater. A long dry spell puts more on a First Flush Diverter. A tank that overflows regularly gets more out of a Tank Vac than one that rarely fills. If you would rather not work that out from a list, our team can talk through what suits your home and where each accessory goes. Call us on 0800 77 66 29, email sales@promax.co.nz, or contact us online for personalised advice.