Pool water issues brought on by tenant

[Gail W.]

My California rental has a very nice salt water pool that we maintain by going over there 1-2 times a week. The entire system was replaced 2 years ago. 

We have shown the tenants repeatedly how to use the system (turn on waterfall, spa, heater, etc...) but they STILL aren't grasping the concept. Many times, they turn the valves the wrong ways, which turns the whole system off. It can stand for up to 3 days before we come and find out it's all off. 

We take the water to the pool stores for testing and always add whatever they recommend. We back flush the system 2-3 times a week (When we lived there, with tons of kids swimming, we did that maybe twice a month!)

Now they are constantly grousing about the water quality. Yes, it's looking cloudy after weekends where they have 6-8 big men swimming in there all weekend, then leaving the system off. The recent testing told us there are too many undissolved particles for chemicals to help. They said just drain the pool half way and refill. The tenants do not want to pay the water bill for that.  All utilities, including water, are their responsibility. Really, I don't mind paying it, as it'll be pretty minimal (I think last time we did this a year ago, right before they moved in, it was an added $30-$40)

HOWEVER...they are getting passive aggressive on everything lately, as they are miffed about a very minor matter. So I'm trying to be diplomatic, yet not be a door mat. 

Are there any rules, as far as water goes, in a rental pool??