Wireless switching relays


I am working on a project where I want to measure the content of a 5000L rain watertank with a differential pressure sensor. I want to use an Arduino Yun connected to my WIFI, to process the measured value and display it on webserver page so I can view it from my smartphone, tablet or PC.

So far no problem, but I want to use the value of the tank to automatically switch over my rain water system. We use the rainwater around the house for the garden sprinkler system and flushing toilets.

What I want is that the system automatically switches over from rain water to city water and vice versa according to the watertank level.

I want to use 2 24V electric valves to switch over using a relay of some sort. Here is where the problem is. The water tank is placed outside and the switching system is inside the house. The arduino that reads the value is inside the garage (separate building from the house) and there is no way to get a wire inside the house that powers the relays and valves.

So I am looking for the best possible way to make a wireless solution. But untill now I haven't found a solution. Should I use RF controlled relay cards ? Some kind of WIFI solution ? A second YUN inside the house that communicates with the one in the garage ?

All suggestions are welcome !

I can think of 3 ways to do it. What you decide will depend on range, cost and what you are comfortable programming.

1) A RF controlled relay. I have used ones supplied by http://www.rfremotech.com which work well. The downside is that although you can transmit the RF there is no way to tell if it has been received.

2) A pair of NRF24L01 modules to transmit over RF at 2.4Ghz and these include handshaking so you can tell the signal has been received. Certainly cheaper than a second Yun as they are a fir bit more expensive than an Uno.

3) Use the built in wireless in the Yun and use a ESP8266 in the house and communicate over wifi. Probably the cheapest option and should work well but a bit more of a learning curve.