How long running water keeps clean?

I was just wondering this, because I read that you should replace drinking bowl atleast every week (I replace water about everyday, so thats no problem) or it gets bacteria or dirty. So what about waterfalls (he loves it :D I dont know is it vibration, but he really likes to climb and hang on it at nights)? My snake never drinks from hes waterfall, but how often should I replace that water for? It is a lot more harder and time consuming to replace that than the simple water bowl.. I think that running water keeps itself clean longer? right?

I hope you got my point from my question :D thanks!

btw. bear grylls says that running water is almost always cleaner than standing :D

If it doesn't have a filter, it'll get dirty just as fast, or faster than non-running water.
It just stays fresher longer because it isn't stagnant.


If it has a filter it should be changed every week or so. Without a filter, every 3 days.