Lookup/Your meter/Water
Water meters — good odds, weak signal
The only meter type that broadcasts something genuinely actionable — a leak flag — and the only one that transmits from inside a hole in the ground.
Read the faceplate first
Water meters live in worse places than gas meters — a buried pit under a lid at the property line, or a basement wall where the service enters. That makes them harder to inspect and harder to receive, but the tell is unmistakable once you know it: look for a wire.
A pit lid with a wired disc or puck in it → likely yes
That disc is the transmitter, and the wire running down to the register below is the giveaway. The radio has been deliberately mounted at the top of the pit because burying it under a cast-iron lid would kill the signal outright. Very commonly a Neptune R900, which is well supported by open tools.
A digital LCD register → maybe
This is the genuine coin flip on the whole site. A digital water register might speak an open protocol, or it might speak a vendor-proprietary encoding that no open decoder handles. There is no way to tell from the display. Look up the FCC ID before buying anything — this is precisely the case the lookup exists for.
Plain mechanical register, no wires leaving the pit → no
No wire, no radio. A full 902–928 MHz sweep at one such address returned nothing but neighbours' meters. Somebody is opening that lid with a hook and reading it by eye.
What it sends
Water is where the protocols get interesting, because Neptune's R900 carries something no other meter type broadcasts.
| Property | Typical |
|---|---|
| Band | 902–928 MHz |
| Commonly observed | ~915 MHz |
| Message | R900, R900BCD, or SCM |
| Interval | Periodic; less frequent than gas |
| Payload | Cumulative consumption plus a leak flag |
| Encryption | None on R900 |
Every other meter on the band gives you a number that you then have to interpret. R900 gives you a field the meter has already interpreted: it tracks whether water has been moving continuously, and raises a flag when it has.
That is a running toilet, a slab leak, or an irrigation valve that did not close — caught before the bill arrives rather than after. Of everything you can receive from a residential meter, this is the one field with a real dollar value attached, and it is the strongest single argument for pointing a receiver at your water meter rather than your gas meter.
Expect a bad signal path
A pit-mounted transmitter is the hardest residential receive job on the band, and it is worth setting expectations before you start blaming your hardware.
- It is in a hole in the ground. Soil is lossy and the ground plane is immediately adjacent to the antenna. You are receiving through a slot at ground level, not from a clear mount.
- The lid may be metal. Cast iron over a radio is close to a Faraday cage, which is exactly why the module is mounted in the lid rather than under it. If yours is a solid metal lid with no plastic window, the signal has to escape around the rim.
- The interval is longer. Water meters transmit less often than gas meters to stretch battery life across a longer service interval. A quiet thirty seconds means nothing here.
Practical consequence: run a long capture before deciding it is silent. Fifteen minutes with no ID filter, ideally with the antenna moved outside and low rather than indoors and high. Where a gas meter gives you an answer in seconds, a water meter genuinely may not.
rtlamr -msgtype=r900,scm,scm+ -filterid=
If your neighbours' meters appear and yours does not, that is a real signal about the path, not about your setup — see only neighbours.
Two registers, one supply
One oddity worth knowing: some properties have a second water meter for irrigation, sub-metered separately so the sewer charge can be waived on water that never reaches the drain. If you find two water IDs at your address and both track your usage, you have not made an error — you have found the sprinkler meter.
Next
Where this leads.