Alec, I use sod. hypochlorite solution labelled "Liquid Chlorine for Swimming Pools". It is labelled "125g per Liter available chlorine." I use a teaspoon in a cup of water in a spray.(posted 8355 days ago)It is normally sold in 4 Liter and 20 Liter containers. I think it lasts reasonably well, but will eventually decompose. Diluted, it decomposes fast, but to benign components.
The brand of household bleach most commonly available here (Australia) is labelled "40g per Liter available chlorine" plus it contains cleaning agents that might or might not be useful in a print washer. I don't know.
Hope this is useful..........John