I grow my camellias in pots and if you want flowers, (why else would you grow them?) you must give them plenty of water regularly, especially in late summer, early autumn, when flower buds are formed. I find you can use tap water from time to time, say one water in 3 or 4. Tap water is better than no water. I have hard water. You can redress the balance with iron sequestrene which will ensure the plants don't get chlorotic i.e. their pipes get furred up and the leaves yellow and fall off. The plants will tell you if they are happy with your water regime.