# Rainwater tanks on toilets: an external pump, a proper filter and a poly tank

Think Water Werribee specs rainwater toilets as one kit: a polyethylene Melro tank, an external (surface) pressure pump beside the tank, a Matelec rain-to-mains controller, and HYDRA Rainmaster Trio on the rain-to-house line.

![Melro 2000 L slimline polyethylene rainwater tank](https://werribee.thinkwater.com.au/products/melro-water-tanks/26-melro-2000-slimline-water-tank.jpg)

![HYDRA Rainmaster Trio rainwater filter kit](https://werribee.thinkwater.com.au/products/white-hydra-filters/19-atl-hydrarainmastertriorah1in.jpg)

![AquaSaver rain-to-mains changeover valve](https://werribee.thinkwater.com.au/products/aquasaver/aquasaver-bas.png)

A lot of Werribee and Tarneit houses already send tank water to the toilets with no filter. Grit, leaf fines and rust from older metal tanks sit in the cistern, chew solenoid valves and stain the bowl. Many existing houses already have an AquaSaver valve on the tank line; if it is sound we keep it and still put Rainmaster Trio after an external pump.

## Why an external pump

An external pump sits on a pad beside the tank, sucks from a low outlet and pushes water through the filter, then the rain-to-mains valve, then the house. You can isolate it and service it without pulling a wet pump out of the tank. Rain-to-mains panels such as Matelec HydroWHIZ and HydroSTART are built around that surface-pump layout.

In-tank submersibles (Grundfos SBA, Bianco AUTOSUB, DAB Divertron) still suit some garden tanks. We do not pair Rainmaster Trio with them.

## Why the filter sits after the pump

HYDRA Rainmaster Trio (ATF-HYDRARAINMASTERTRIORAH1IN, White 807344): 90 micron stainless mesh, then 25 micron polywound, then 10 micron carbon block, 1″ BSP. For toilets, laundry and gardens. Not drinking water unless you add UV. The kit wants at least 1.8 bar, which a surface pressure pump can hold.

## Metal tanks rust. Poly tanks do not.

Galvanised and corrugated steel tanks rust from the inside. Flakes stain toilets and chew rain-to-mains valves. For toilets on rainwater we spec a polyethylene Melro tank. Metal tanks can still make sense for some fire or farm jobs; they are the wrong vessel for a toilet rain-to-mains install in Werribee.

Human page: https://werribee.thinkwater.com.au/guides/rainwater-tanks-toilets-werribee
Tanks: https://werribee.thinkwater.com.au/rainwater
External pumps: https://werribee.thinkwater.com.au/pumps?range=domestic-pumps&category=MP%20Multistage
Rain-to-mains: https://werribee.thinkwater.com.au/pumps?range=matelec
AquaSaver 20 mm and 25 mm: https://werribee.thinkwater.com.au/pumps?range=aquasaver
AquaSaver 20 mm product: https://werribee.thinkwater.com.au/products/aquasaver/aquasaver-20-mm-rain-to-mains-valve-aquasaver20
AquaSaver 25 mm product: https://werribee.thinkwater.com.au/products/aquasaver/aquasaver-25-mm-rain-to-mains-valve-aquasaver25
Rainmaster Trio: https://werribee.thinkwater.com.au/products/hydra/hydra-rainmaster-trio-rainwater-kit-atf-hydrarainmastertriorah1in