All of this liquid will eventually go into your product. If you are using balanced O-ring seals you will only need enough liquid to remove solids that might interfere with the seal movement. You will not need additional liquid to provide cooling because balanced seals do not generate enough heat to cause problems in most applications. If you are using designs with multiple springs in the fluid check with your manufacturer for his recommendations. One of the ingredients in the product Finished product will never hurt raw product.
Finished product is almost always clean.
An additive that is going to be put into the product down stream and can be added at the pump stuffing box instead. If you are using shop water as the flush you must be careful or solids in the flushing water will clog up the flow control valve. The shop water pressure also tends to vary through out the day and in some instances it can fall below the pump stuffing box pressure. Most states require an air gap in the line if you want to use shop or city water as a flushing medium. A back flow presenter valve is used many times but it is illegal in most states.