I do want you to know I do not use it with kalkwasser. It doses RO/DI water for makeup water and I dose concentrated kalk from a seperate container. The AT1 will not be effected by kalkwasser, but a pump will. I'm sure it would work well as long as attention is paid to the pump.
I used one of these for a year on my 55 to refill Ro.
Never had any problems with it at all. The pressure tube does not come with a mount so you will need to make your own. DO NOT use a suction cup. securely mount it! If the tube is mounted with a simple suction cup and comes loose (as always happens over time) you will have a flood. I can personally attest to it as it happened twice to me before I got smart and mounted it with a zip tie. If its any help here, I took an empty plastic film canister from a 35mm roll and screwed it to the inside of my canopy, popped two holes in the end of the cap and threaded a zip tie through the holes and ratched down the tube to the cap. The cap can then be popped off if you need to remove the canopy and the film can will still be mounted to the hood for replacement.
HTH