I bought some Aurora zigbee double sockets, but switching my pond pump killed the relay in a couple of weeks. Shout out to Smart and Secure for replacing it for free, but I’m on the hunt for a device to use instead to switch the pump that I could put in an IP-rated junction box. Any suggestions?
I’d prefer zigbee, but z-wave or 433 MHz are possibilities. Don’t want WiFi if I can help it…
Hi,
I’ve installed a similar automation for a friend with a large pond, rill, UV filters, and several pumps in the UK.
A Sonoff 4CH v2 with several additional DS18B20 temp sensors on a GPIO work well running Tasmota - but all use WLAN. Logic to not run the pump when the air / water temperature drops can be run on the Tasmota ESP or HASS. The kit is mounted in a plastic sealed box, fed with SWA armoured cable (which still can get damaged and such water in tripping RCBOs).
The easiest to get in the UK is likely a Sonoff TH16 - again, WLAN, but 16A, and has the socket for temp sensors built-in (chop the leads if you want multiple sensors for water depths and air temps).
As some pumps are inductive (often AC synchronous), a snubber network might be worth adding if you are switching many times a day (small R-C network potted into one, used for interference suppression).
If you’d ever run RTL-SDR and looked at the junk transmitting on 433MHz, you’d avoid it like the plague! My friend picks up his oil tank Watchman sensor (and another used as a pond depth / level sensor), a neighbours weather station, and about 10x battery doorbells around the village.
Sonoff or Shelly are the easiest and safest kit in the UK for light customisation. They run ESPs with lots of instructions to remove the crappy cloud firmware (well, Shelly is all local and decent these days…) for ESPhome or Tasmota.
Sonoff are just starting Matter device release, although in this case that is really only WLAN with a different protocol than MQTT.
If this helps, 
this post!