said by iknow:
no, the amount of harmful bacteria etc. is much lower in cold water, so much lower that the governing body of the water agency you get the water from deems it safe to use!. it's the vastly increased amounts of bacteria etc. in WARM water that makes it unsafe, they grow to dangerous levels in WARM water!!. have the condensate from your A.C. tested sometime!!.
Its not that there is "more" contamination in warmer water, it is the combination of the water being stagnant (i.e. hot water tank) and being in a warm environment that promotes the growth. If you take water from the same source and put it in two sealed containers, one room temperature and one warm, the warmer will grow faster but the room temperature will also grow, albeit slower.
Conversely, if you take room temperature water and warm water (120 F) and circulate both in individual closed loop environments you'll probably see negligent additional growth in the warm water loop vs the room temperature loop - the water is not stagnant, you've broken the cycle (think breaking fire triangle).
Circling back to the actual problem and original post, its the combination of the bacteria being present (which it almost always is) and using that water in a Neti pot. It doesn't matter if your water tank is set to 160 or 120, when you take that water and expose it to the thin membranes of your sinuses there is mounting evidence that you expose yourself (unnecessarily) to a greater risk of infection. What's not known is how many times someone has used a Neti pot, got infected and not had a severe enough reaction to have the incident reported - or for that matter, how many times a Neti pot is used and no infection occurs.