on edit: changed a no to know, was multitasking.
What exactly do you expect a medical professional to do here?
There’s definitely a problem with a child wasting resources without being able to be stopped.
How is there not a problem here?
1. nonverbal, which makes dealing with issues difficult and time consuming.
2. and has a number of problematic behaviors that might actually be more worth focusing on than their wasting water, since it is often difficult to fix multiple behavioral problems at once when dealing with autism.
at any rate, if it takes him half a year to get off of wasting water I would like to have a temporary fix in that half a year as well. Sometimes it's better to ship a quick solution than to wait for the perfect one, losing money the whole time.
Some water pump models will break if they do not pump water but air. Only buy pumps which are able to handle air in take.
Nevertheless, and I hope this sounds constructive, this is the kind of topic that you should really be discussing with an occupational therapist or child psychologist with experience in autism.
For some topics the internet can be a terrible place for advice.