A rain to mains system lets a house or small building use tank water for toilets, the laundry and the garden, and switch to mains water automatically when the tank runs low. The tank gets used first, and nobody has to remember to flick a valve when it runs dry.
The rain to mains range PSA stocks covers four different ways of doing the changeover. They suit different pumps, flows and mains pressures, and they don't all behave the same in a power cut.
1. Hydraulic changeover valve
A hydraulic valve sits after the pump and switches between pump and mains supply with no electronics in the changeover. It's the simplest option and usually the cheapest.
- MaxiSAVE MHR20 ($314.55 valve only): solid brass, over 50 L/min, 500 kPa maximum mains pressure and 600 kPa maximum pump pressure, 25mm rainwater inlet with 20mm mains inlet and outlet. For household toilet and laundry supply.
- MaxiSAVE MHR25 ($666.55 valve only): 25mm BSP connections, over 200 L/min, 1050 kPa maximum mains and pump pressure, a certified dual check valve for backflow prevention and a 3-year manufacturer warranty. For higher flow homes and small commercial sites.
- Bromic hydraulic changeover valve (7575029, $276.05): low lead brass, with manufacturer-stated WaterMark approval to WMTS 477:2016 (licence 021636) and a 5-year replacement warranty. Pairs with Bromic's 3kW pressure controller and jet pumps.
MaxiSAVE also sells the MHR20 and MHR25 as packages with a Hyjet or Pedrollo pump, labelled by the number of taps they suit (for example, 4 taps for the JCRm 1A-EP1 package or 10 taps for the 5CRm 100-EP1 package).
2. Electronic controller (MaxiSAVE RM1000)
The RM1000 ($1,062.55 kit) uses a 10m, 24V float switch in the tank and a pre-plumbed manifold with a 20mm solenoid, a 20mm dual check valve and a 25mm single check valve. It prioritises tank water, switches to mains on low tank level, and per the listing switches to mains on power failure too. LEDs show whether tank or mains is in use, and it draws less than 100 mA.
That power-failure fallback is the main reason to choose it: if the power goes out, the toilets still flush. It's sold on its own or packaged with a Hyjet HSJ jet pump or HCM multistage pump. At listed prices, the RM1000 packages are $193.55 to $281.55 cheaper than buying the kit and the same pump separately.
The RM2000 and RM4000 systems take this a step further, with a Hyjet pump, controller and valves pre-plumbed in one poly enclosure (705mm high, 500mm wide, 400mm deep) for larger homes and irrigation.
3. Top of tank assembly (MaxiSAVE MTA20)
The MTA20 ($545.55) mounts on top of the tank and is built for submersible pump systems. It's hydraulically operated, solid brass, with a built-in dual check valve, a maximum flow of 50 L/min and a recommended maximum mains pressure of 500 kPa. It's also sold with a Hyjet HSM6-40A submersible pump (MTA20-640S). A 2m hose connection kit is available separately.
4. Integrated rain to mains pump (Hyjet HHR)
The Hyjet HHR combines the pump and changeover in one unit. The HHR-400 (370W) and HHR-550 (550W) draw tank water first and change over to mains when the tank runs low or the power fails, with run-dry protection. Both are available pump only or in a Polyslab cover with two flexible hoses. Note the 200 kPa mains supply limit: if your mains pressure is higher, fit a pressure limiting valve or choose a different system. The HHR-370S is a submersible version (370W, up to 45 L/min and 28m head) that sits in the tank for quiet running, with a float switch included.
How to choose
- Measure mains pressure first. It rules options out: the HHR is limited to 200 kPa, the MHR20 and MTA20 to 500 kPa, and the MHR25 to 1050 kPa.
- Decide on power-cut behaviour. If toilets must keep working when the power is out, choose a system the listing says changes to mains on power failure (the RM1000 and HHR).
- Match the flow. A couple of toilets and a washing machine are well within 50 L/min. Several bathrooms plus a garden tap running together may need the MHR25 and a larger pump.
- Surface or submersible pump. Submersible pumps suit the MTA20 or the submersible packages; surface pumps suit the MHR or RM1000.
- Filter the tank water. An inline filter between the tank and pump keeps debris out of the pump.
- Backflow and installation. Rain to mains systems connect to the drinking water supply, so they must be installed by a licensed plumber to AS/NZS 3500.1 and your local authority's backflow requirements.
For choosing the pump itself, see our guides to household pressure pumps and multistage vs jet pumps. The MaxiSAVE and Hyjet systems are available to order on backorder; contact PSA to confirm lead time.
Frequently Asked Questions
Does a rain to mains system work in a power cut?
Some do. The MaxiSAVE RM1000 and the Hyjet HHR are listed as switching to mains on power failure, so toilets keep running. Check the listing before relying on it for other systems.
What mains pressure can a rain to mains valve handle?
It varies. The Hyjet HHR is limited to 200 kPa, the MaxiSAVE MHR20 and MTA20 to 500 kPa, and the MaxiSAVE MHR25 to 1050 kPa.
Do I need a plumber to install rain to mains?
Yes. It connects to the drinking water supply, so it needs a licensed plumber and must meet AS/NZS 3500.1 and your local authority's backflow requirements.
Is a package cheaper than buying the valve and pump separately?
For the RM1000 kits, yes: $193.55 to $281.55 cheaper at listed prices. Some hydraulic valve packages are not, so compare the package against the separate prices before ordering.