Since the craftsmen mainly use an engine from a service machine washing machine (CMA), I suggest breathing in a second life with no less useful details, namely:
drain pump
level sensor
inlet valve
and drum
The first thing we can do is, using a level sensor and a valve, to assemble the simplest device for collecting water into a container, i.e. if the water supply is connected to the tank, we assemble a simple circuit to maintain a given water level by connecting the level sensor and the valve in series.
If the water supply is not connected, i.e. there is no water pressure to operate the valve; instead of the valve, you can turn on a warning lamp or an audible signal about the filling of the tank.
Next, we use the pump, namely, connecting it to the tank (we connect to the bottom of the tank, from the outside and by lifting the outlet hose above the water level to prevent self-draining) and using the timer, you can do periodic watering at specified intervals.
For the next homemade, the electrical part must be isolated from moisture by simply filling it with epoxy
Assemble the pump
Having lowered the assembled pump into the water, we will check its performance by connecting it to the network via an RCD
After making sure that the device is completely safe, we proceed to the main target, namely, we will assemble a fully functional circuit for pumping waste water.
We dig in the tank from the SMA, inside which there is a level sensor with a tube brought out to activate the relay, and connect our now submersible pump through the sensor relay to the network.
Using this sensor turned out to be more convenient than a float from a submersible pump, because there are no moving parts, and the retention of a given water level is in a narrower range.