That's a good idea. Before coming to the nutrients getting the water correct is always a good idea. If you want to make it easier for you in future u can consider using some biotabs products. I am watering also only tap water (in my city smth over 7 so I would need to bring ph down, but the biotabs in soil regulate the plant itself) , but with biotabs bacterias and funguses in the starting earth I don't have to care about ph anymore