In this series of posts of common items found on my inspection reports, I can sum up findings in various parts of my report under the concern of drinkable water mixing with gray water. Gray water being any water that has been used and thereby contaminated with cleaning products or other items.
Anti-siphon devices on hose bibs (which are the exterior water faucets) seem to come up on older homes. This stops water from coming up the hose into the house’s plumbing system. You can buy the part at a hardware store for around $2. It screws onto the bib like a hose would. No special tools or other parts needed. The point where water exits the faucet or fixture should not be below the water line of the container for the water. Say you have a bathtub where the faucet comes down into the tub area where the water is held. The dirty water then could go into the faucet. For tubs this is not common, but I have seen it for wash sinks, and in toilet water storage tanks. There should be at least a one inch air gap between the tub and faucet. The last common place for water to back flow is the dishwasher. There will be a hose coming from the dishwasher to the drain system for your kitchen sink. The hose should be positioned so that it has a high loop up to the basin then comes down for its connection point. A twist tie or other such fastener can assist in keeping this hose in place.
There is one device that will have a contamination point built into the unit, but you do not have to worry about it. A water purifier is designed with such a contamination point, but it will not cause a problem. The system functions because of this access between the water.