Unless you are part of a jurisdiction that allows for combined sanitary and storm systems, you cannot connect the discharge of floor drains and sinks to a storm outlet.
Storm drainage does not go to any treatment works so even though grey water does not contain human waste elements, it still can contain elements that are not proper to be discharged to the environment without treatment.
Also, we all know that sometimes things that go down a sink or is dumped into a floor drain are not necessarily something that should be - which if it goes to a storm system can be a real problem. It can be a problem for a sanitary system - but at least then there is some treatment prior to going to the river or whatever discharge point is relevent.
There shouldn't be an issue with connecting floor drains and sinks to a sanitary cleanout - as long as the cleanout fitting is changed to an appropriate drainage fitting (sanitary tee or wye/45)
The question is not what you are answering. I did mistype the information, as the grey water does go to a maceator, but forget about the jurisdiction, etc. This is an industrial application with special circumstances. The question is on the long unwashed horizontal grey lines going to the cleanout on the wall.What is the situation that develops when you have long unwashed lines.
Without knowing what is going down the floor drains and sinks - it is difficult to predict. If it is just drainage water or normal floor drain or sink drainage - you shouldn't have problems with unwashed pipes.
The problems occur when there are solids that might settle out or any kind of organic/biological residue that might yield some kind of growth of slime or something similar. That dries out and your piping starts to be become constricted.
Think about the drain of your sink. If you have ever taken the trap off - there is always a layer of slime buildup in the drain pipe going into the wall. This is typically always wet because it gets frequent flow. But imagine that build up dries up and you will see what I meant.
The next batch comes through - more slime builds up, dries out and after many iterations, you lose significant pipe diameter.
That answers the first questions - but I wonder why you can disregard the jurisdiction. I was not aware that the plumbing code does not apply to plumbing fixtures in an industrial system.
A maceator does physical treatment (breaking big things down to smaller things) - but does not treat the organics or biological constituents. If the industrial setting has its own treatment works which takes both storm and sanitary discharges - then all is well.
