Loud enough and stable

I wanted to monitor the lifting station in the basement with a water detector to be warned in time with any leak or failure with subsequent water leakage.
Since the lifting unit has pump away only the condensation of the heat pump, overflow of water softener and wastewater from washing machine and sink economy, the risk of long unseen damage is given only by the heat pump. (In case of failure of the lifting unit during a wash load one would notice the problem at the latest after a load of laundry, when using the economy sink immediately. The overflow of the water softening system is only used when a problem of softening, meaning it occur then have damage to two devices at the same time.)
The amount of condensed water of the heat pump is relatively low, so that no great damage can be expected.

That's why I was looking for a stand-alone water detector, which should be beneficial, but should reliably hit even with small amounts of water.
Many devices offered here has been criticized that the devices "float" and strike only at relatively high water level. This problem did not seem to be given by the vertical up configuration from the device now purchased, additionally, is a cable sensor which can be used in addition to the built-in contacts, available.
The siren should be loud enough to be heard at least on the ground floor safely. With the dB indication this was not clear, as the same volume of other devices in many reviews was "barely perceptible" criticized as.

After today I can start both the volume name to be entirely adequate and reliable warning of low water level.

In addition, an advantage for me that this unit is powered by (3 pieces) AA batteries instead of a 9V block. It is true that in the manual explicitly stated not to use batteries, but I have to run before the unit with Eneloops once the supplied batteries are empty. Let's see if this works, the battery life is reported to be about 1 year, it should be warned about 2 weeks ago finally discharged batteries. If the warning strikes, I will measure the residual voltage of the batteries and then decide whether Eneloops can work or not. More on this in about 1 year :-)