Guide · Rainwater tanks
A cistern and rain tank water monitor
Rainwater starts soft and clean, then picks up whatever is on the roof and in the gutters. A monitor on the tank shows what each storm brought in.
BlueSignal · October 9, 2026
What changes in a rain tank
- Turbidity rises when the first flush is missed or the screen clogs.
- Rainwater starts slightly acidic, so pH tells you how it is reacting with the tank and the roof.
- TDS stays low in clean rainwater; a rise points to something dissolving into it.
- Temperature tracks how the tank sits in the sun.
What the monitor reads
The WQM-1 reads pH, TDS, turbidity and temperature every 60 seconds and shows them in BlueSignal Cloud. A notification on your phone when a reading moves.
Sizing the tank first
The free tank calculator and the Rain Planner size a tank from your roof and your rainfall, and list rebates that may apply.
Drinking rainwater
Drinking use depends on the treatment after the tank and on local rules. A licensed plumber and your local authority decide it. Read the drinking-water guide for what treatment involves.
It does not test for bacteria, nitrate, arsenic, lead or PFAS. Those still need a lab test, and the PFAS check shows what EPA has on record for public systems near you.
Questions
Where does the monitor go on a cistern?
On the outlet line from the tank, before any treatment, so it reads the water the tank holds.
Does it work on a metal or plastic tank?
Yes. It reads the water in the line, not the tank wall.
Does it check for bacteria?
No. Bacteria need a lab test.