Water Supply Automation (aka Smart Meter)

[MortarThePoint]

There are various products (e.g. Moen Flo) on the market that effectively include the following elements:

1. Wireless brain with some combination of WIFI, Zigbee and Bluetooth
2. Motorised valve
3. Flowrate sensor
4. Pressure sensor

 

It's a deal breaker for me to have something that requires a subscription (ongoing cost, dead device when cloud disappears,...) and most of the off the shelf ones are such. Consequently, I am tempted to roll my own and have identified the following parts as good options:

1. Brain [£10] Lots of choice, ESP32 likely candidate. Relays likely needed to control mains voltages ... needs more thought
2. Motorised valve [£30] You don't want a spring return one as that would require constant powering and also cut off your water whenever there was a power cut. There are various cheap options on the likes of Amazon (link) but they won't be WRAS approved. You can also get retrofit actuators (link) that operate an existing lever valve though these look like they would struggle with a stiff valve, but that approach does resolve the WRAS requirement. You can get wireless connected valves (eg link) that would allow connection to a home automation system to close the loop.
3. Flowrate sensor [£50] There are plenty of off the shelf meters with digital pulses.  For example this one from BES that does 1 pulse per litre. Would be WRAS
4. Pressure sensor [£20] I haven't found one that is approved for drinking water (e.g. WRAS approved), but this is the sort of thing: https://www.dfrobot.com/product-1675.html

 

A bit of elbow grease and some additional fittings and you can make your own system for around £100 that wouldn't go obsolete.

 

The pressure sensor is the main issue at this point as it is required for leak detection (shut off water and see if pressure drops) but I haven't found one that is WRAS approved of claims to be OK for drinking water.

[MortarThePoint]

Two considerations on leak detection are:

   a) cracking pressure of check valves: if measured up stream of check valves, a leak down stream of any check valve needs to lower the pressure enough for any check valves to open. I don't know the exact cracking pressure of check valves, but I would guess they are a fraction of a bar.

   b) supply pressure variation: not an issue as supply is isolated during a leak test. It does affect the working range of the sensor though. I'll have a PRV (pressure regulating valve) set to something like 5 bar (hopefully).

 

I don't know how much of a pressure drop is considered a leak by the likes of the Moen Flo. I could conduct some tests, but my gut feeling at this point feels like a 0.5bar drop across 5 minutes would be a reasonable threshold.

 

One retro fit option for a pressure sensor is to use a camera to observe the pressure gauge of the PRV. An ESP32 could WIFI an couple of images to a PC for analysis.

 

[MortarThePoint]

Does anyone if these water meters are noisy?

Pulsed Cold Water Meter - 20mm, 3/4" BSP TM

The Pulsed Cold Water Meter (20mm, 3/4" BSP TM) is designed for accurate monitoring of cold water consumption, typically linked to energy monitoring systems. Featuring a 20 mm nominal bore and 3/4" BSP TM thread, this meter ensures precise measurement with a pulse rate of 1 pulse per litre. [https://www.bes.co.uk/pulsed-cold-water-meter-3-4in-22976/]

Edited 4 hours ago by MortarThePoint