Water Question

Hi all,
Just wanted to ask a question about how you all use your water. We usually bring bottles of water with us, we pick up 5 or 6 when buying our food and use this for drinking, making tea and cooking. Is this the norm? I cant imagine consuming the water from the tank is hygienic? No matter how clean it would appear there's always some remaining stagnant water-currently ours is parked up for almost 2 weeks with about a quarter tank and its been pretty hot the last few days...
We made the mistake on our first trip away using the water we filled from the site and a slight green tinge with a nettle aftertaste soon made us rethink! But it also got me thinking while bring this extra water is fine for short trips how would one manage on a longer trip with perhaps a few nights of wild camping thrown in?

We used to use bottled water for drinks, cooking, making tea, however we found that the tea didnt taste as nice and the water was leaving a residue in the kettle. So we changed to using the tank water for boiling but still bring bottle water for drinking (particularly for the kids).

We also clean the tank (not so regularly ). Also, we have a valve on the tank so we empty the tank every time we get home. However, if you decide to do this just remember to turn off the pump.

Clean our tank regularly with a weak Milton solution, run thru the taps to the waste tank to clean pipes too.
Rinse well with fresh water.
We use water all the time direct from the tank....... reasoning if it has travelled many miles through mains concrete pipes/plastic pipes and in lots and lots of cases there is still asbestos and lead pipes still being used in water Mains then a clean tank in the van shouldn't present any problems.
We do drink sparkling water from Asda or Lidl/Aldi in lieu of of soft drinks bought in 6x 2 litre bottles.

We use a ten liter refillable can for cooking etc and buy bottles for drinking,the tank in our van is only used for washing because some of the areas visited may not have drinkable water.

During the winter I use the water from the tank for drinking and cooking etc. The tank is then emptied and refilled for each weekend. I would be reluctant to use it in the summer months as residue from the previous week is in the tank and then topped up. I was using the 5 litre supermarket bottles last summer but I did not like the taste in coffee etc and there was always a grey layer floating on the coffee. I saved a few containers and refill these at home to bring with me.
Last summer I filled the van tanks on a site using a brand new cheap 10 metre hose purchased in B and M. The ends of the hose were sealed and I cut them opened to put the attachments on before filling. Later in the day I thought I could smell a chemical smell and by morning the water smelt like Jayes Fluid. I dumped the tanks and researched a cleaner, many recommended Milton but advised that it may corrode stainless steel pipes and tanks which Alde wet heating systems have, those with Alde heating recommended the Halford version which worked well for 3-4 quid.

3 5ltr bottles for drinking and tank for washing dishes