Idea's for ATO and SW change containers.

[mark]

Go to a plastic tank supplier (eg here) and you can get a tank of any shape and size then build around it. Tank can be sealed or externally vented to control humidity. ATO through your PLC and floats, level sensors or might be able to find the type of probes used in travel trailers for the black and grey water holding tanks.

An idea, I had a bunch of the plastic storage totes (about the 20g size) I wanted to get out of sight so I built a bench over them. Have about 10 of them along one wall.