300 Ppm with DWC

This depends on what’s in the tap water. I don’t recommend using tap water for DWC. I personally use RO water. DWC is best starting with as low as a PPM/EC as possible so you know what your plants are eating and your actually feeding it. Yes you can probably get away with growing in DWC like that if you let all chlorination burn off. Me seeds and clones start at a PPM of 300 (500 scale/EC 0.6 ) so a starting ppm of 250 or more is considered hard water for most hydroponic setups.

I'm all in with Chow_13's comments here... that's the beauty of DWC - if something isn't working, you can change it instantly... Try using your tap water and just allow for the increased EC due to the ppm of your water... if the plant struggles, you can switch to RO or Spring Water but right now you don't have to commit to that expense. Good luck!

Yes you can use. this is normal. usually in tap water from 200 to 300 ppm. depending on the country and region.

If you have a good access to RO or the resources to use it - go for it. Be sure to run a cal mag supplement if you choose to use RO.. Good to use it regardless but definitely if you use RO

I have 160ppm so I have no practical experience and this is based on what I have read. Anything over 200 is not recommended but I have also read of people growing in 500 ppm tap water and had no issues. You could always try it out and if you start getting negative result's then switch over to RO water. It would be hard to tell if your doing dwc for the first time because of how picky hydro is. One PH swing and you can get some funky leaves. Happy Growing