We’ve all done it. I would say to myself, “I’m going to remember to shut that valve off”. It was usually on one of my pools that I needed to add water to and would turn on the fresh water valve (with a backflow preventer) to fill the pool. Then the normal routine would set in, the next phone call, a guest wanting to check out, a restroom has an emergency, somebody just backed over an electric pedestal, etc. And lo and behold, the next thing I would do is go by a pool that was overflowing. It had completely slipped my mind.
I found a very inexpensive solution to my problem. I bought some of those plastic coiled wrist bands and attached a plastic tag to them. I labeled the tag and draped it on each valve so whoever turned on the valve had to wear the “bracelet”. I obviously was not concerned with attempting to make a fashion statement but it stopped 99% of the, “Oops, I forgot”.