I thought I would mention something that our oncologist told us when my husband's neutrophils were very low.
Even though public water is somewhat purified your water supply may very well be like ours. Our oncologist told Don not to drink tap water as there are still impurities in it that could harm those with weakened immune systems. I went to our county utilities web site and it had the same type of warning as you get at restaurants concerning raw food and compromised immune systems.
I stopped drinking out of the tap long ago. We have a filter on our refrigerator and use that for coffee and drinking at home and keep bottled water to take out.
It may be something you want to look into.
God Bless,
Sally