Wilting leaves would be an indication, but otherwise just pay attention to the potting mix itself. If it is dark/cool to the touch below the surface there is water there for the plant. Early in the season containers seem to never go dry, but once the heat of summer comes and the plants are large it's a completely different story.

I will give you some very general suggestions. I water mine weekly in hot weather. In nature they only get what nature gives them. I don't where you live, so it's difficult to give instructions. They are native to our south west states. The soil is well draining, and we do water once a week, except during the winter months. Never grown inside. I also give a low non nitrigen liquid fertilizer. 2-10-10 to encourage flowering. I do not grow this species at home, only at the Huntington Gardens. Just my luck I would fall into the plant. LOL Norma

There is a lot to be said here but I will restrain myself. For only charcoal filtration, any faucet should work. Use a charcoal filter that is standard size (guessing without moving my keister to measure that standard means 3 inches in diameter by about 10 inches long.) Pressure drop should be modest until depleted so flow would be high. With R.O. water, one needs a pressure tank and at least 3/8 poly tubing to use with a standard faucet. One may also need other active components to keep the pressure up. My R.O. system feeds a Brizo Venuto, a Brizo pot filler, a plant wand, a refrigerator ice maker, and eventually a bar sink faucet. However, I have a peristaltic brine-driven pump from Spectrapure, and two pressure tanks. With R.O. filtration, it is possible in some cases for the resulting water to become soft and acidic, and this can leach lead where present. For such cases, a lead free faucet is needed. My R.O. input is municipal water that has been dosed at the source with alkali chemicals, and pH measurements show that it is still alkaline after R.O. filtration. kas

You can't water on the basis of volume per unit time Just doesn't work that way. It depends on the drainage and the evaporation rate (which depends on heat, humidity, and wind). What you need to do is be able to recognize the difference between moist soil (no, not drippy, soggy soil) and dry soil. Plants want the former. Many people seem somewhat challenged in trying to figure out if their soil is moist, and end up getting it sopping wet as a result. Moist soil is darker than dry soil, and it is perceptibly cooler. It is not muddy. It doesn't look "wet". I like the advice about soil being dry down to your first knuckle. I pretty much do exactly that. I stick my finger in and see what it feels like. Yes, keeping the surface moist just invites problems with bacteria and fungus, but several inches of really dry soil will kill roots. If your soil is moist below the first knuckle, and you have yellowing leaves, you have some entirely different problem. Through the caveat to that is that some plants, such as mint, really do like moist-to-the-surface soil. In fact, if you over-water (certainly for peppers and tomatoes), your first sign of that will probably be yellow leaves. I suppose another caveat to that could be if your bed was shallow, and not dug well, such that the roots are all near the surface.