In my 15 years of servicing restaurant hood sytems I have never seen a wash water hood system that is worth its weight in grease.
Problems I see with wash water systems----->
The nozzles only clean in a set direction, the rest of the area is not reached by the nozzzle becomes contaminated
Once the chemical resevoir runs out it is rarely if ever refilled on a reasonable basis.Then you have nothing but water pushing grease and contaminents around inside the hood over the cooking area.
All the contaminents that are removed by the nozzles end up laying in the bottom of the track. Wich in turn accumulates and creates bacteria.
The drains are usually plugged at one location or another be it at the beginning of the track or somewhere in the pipe along the drain system.
They break down and do not get repaired.
I have heard many times. We have a wash water hood system ,We do not require a hood cleaning service. Then I proceed to show them what the interior of the hood looks like. I get alot of EWWW Yuck thats nasty.
Then I proceed to explain to them how it only cleans the area in front of the nozzles and not the Filters the Plenum the Duct of the Fan.
In fact those with wash water hoods need to be in contract with a experienced hood service as to avoid bacteria build up and a serious fire hazard.
So- in conclusion, Explain the down falls of the system and sign them up for a regular service. It would be benficial to there environment and your business.
In my opinion the wash water hood sytems should be replaced with a regular Type 1 Hood with out any wash water system.
Oh and get the part, not that its going to actually clean the hood but if they want to pay you to fix something thats obsolete then have at it.
Just my 2 cents. Cheers GOAT.