All dry to dry machines have a water separator. Perc machines are equipped with one separator, while a good number of hydrocarbon and Green Earth machines will have two separators. It is in these separators that the solvent that is recovered in the drying and distillation processes is collected. The solvent that is collected will contain water. The water must be separated from the solvent and disposed of, while the solvent is returned in pristine condition to be used again in the cleaning process. (For those not in the dry cleaning industry, dry cleaners are essentially recycling their solvent and returning it to "like new" condition to be used again. This process is repeated over and over allowing dry cleaners to clean huge amounts of clothes with very little solvent actually being lost in the process).
Solvent and water are separated by the effects of gravity, in which the heavier liquid settles to the bottom of the separator and the lighter liquid will rise to the top of the separator. With the specific gravity of perc being much heavier than water, the perc will settle to the bottom in perc separator's, while in the case of hydrocarbon and Green Earth, these solvents are lighter than water and will rise to the top of the separator.
Some other factors that can affect the separation process are:
- Temperature of the Solvent and Water being reclaimed. Separation occurs more efficiently at cooler temperatures. If solvent/water is too warm you may see only partial separation, the separator may look hazy or cloudy and solvent may be lost due to this poor separation. (Note: in machines with two separators, hazy/cloudy solvent is normal in the first separator, but not in the second separator).
- Reclaiming too Fast. This is quite often seen as a slight "boil over" of the still. Solvent is being reclaimed so fast that there can be a disturbance in the water layer of the separator. The separator my be filling so fast that there is not enough residence time to allow the solvent/water to separate completely.
- Separator is Too Small. There are a few machines that have been manufactured that have a water separator that may be undersized. This does not allow enough residence time for adequate separation and the result is solvent being returned to the machine mixed with a small amount of water.