A little about baking soda and epsom salt for reconstituting water.
1 gram of baking soda will increase the kH of 10 gallons of water by 1 degree. 1 level teaspoon weighs ~8 grams (+/- 0.5g). It dissolves readily in water – i do my additions right in the RO barrel minutes before water changes.
Espom salt (and your gh) really dont need to be that high in tanks. I reconstitue to about 14ppm GH (1 teaspoon per 10 gallons).
If one were inclined – you can acquire a small jewelers type digital scale on ebay for 20-30$. You dont need one that does more than 100 grams, but do try to get one with +/- 0.1gram sensativity. +/- 1.0 gram will work for most aspects of aquarium keeping, but when working with smaller quantities of water this extra accuracy will come in handy.
For those using larger barrels to r/o holding do know that a standard mechanical float valve shutoff is acceptable for your barrel. Shutting off the production line will just cause the membrane to stop passing liquid thru and put the full flow out the waste line. Some company’s will try to sell you a drinking water kit for $30 or more, but everyone i’ve questioned says this is un-necessary. The only drawback to this – if you’re paying for munincipal supplied water – this can get expensive so you still have to remember to shut it off … this will only stop overflows on your barrel.
If one were so inclined a float switch can be installed instead of a mechinical float valve, and connected back to a selanoid cointroller on your r/o’s main supply line. This will alow you to pretty much have the ultimate controll over your system – and not waste any extra water when your barrel fills up to the desired level.
One more side note about maintence on RO systems. When you change your membrane, you need to empty your barrel and give it a good scrub. Over time a film will develop and this needs to be cleaned up. Once per year seems to suffice to keep under controll. Sadly this makes it so your barrel has to have the top removed or at least a good portion of it cut off. Clean the barrel as you would when scrubbing out an aquarium, and RINSE RINSE RINSE if you use any chemicals for cleaning.