400 litres into my hot tub topped up with our hard tap water = sheer bliss. (and less nasty chemicals)
Have just had 60 minutes with cold beer and top tunes. the perfect way to wind down after a hard day windy washing
Tried this last year in my hot-tub
you will find that your water will get muckier far quicker and also the water will be too soft and damage your pump it might also strip the sheen off the fibreglass finish (this is what i was tld from the company that i bought it from)
stick common garden tap water for best results
Mines been shut down over winter but reading your post is giving me itchy fingers to go fill her up lol
for some reason a glass of cider dosnt taste the same sat here in the house as it does sat in the tub