By Doug Wallingford
“Open” or “closed” applies to more than zippers
Fresh water is the key difference between divergent types of plumbing systems
One word can have a huge impact on the proper functioning of your commercial plumbing equipment.
The commercial plumbing equipment business is full of terms that may be commonly used but not necessarily understood. One question I get fairly often is: “What is an ‘open’ system?” This question usually is prompted by a reference to an “open” system or a “closed” system in project or product specifications.
Of course, these words are antonyms – two words that have opposite meanings. To the layperson, however, their definitions, as related to commercial plumbing systems, may not be as obvious. After all, the average person may look at their residential water heater and think: “This must be a ‘closed’ system because all the connections are sealed, and the water flows one way. Wrong answer. Thanks for playing. This is an example of an “open” system. Why?
An “open” system is defined as one that receives a constant or somewhat regular supply of fresh, oxygenated water (potable or otherwise). Of course, we need fresh water for drinking, washing, irrigation, etc. So what kinds of systems don’t need fresh water? “Closed” systems.
A “closed’ system reuses water for long periods of time, with no further (or a very slight) infusion of fresh water. A “closed” system is initially filled and then closed, hence the name. A radiant heat system that heats water in a storage tank or heat exchanger and circulates it through a looped circuit of pipes is one example of a “closed” system. But no matter whether it’s an industrial boiler or a residential heating system, the criterion is the same: If the system does not connect to an outside water supply, it is a “closed” system.
In an “open” system, the oxygen in the water, and its reaction when exposed to the catalyst of heat, contributes to potential corrosion of the system’s components. Therefore, all components should have superior corrosion resistance and may be made out of non-ferrous metals (like brass, copper or bronze) or stainless steel, titanium, etc. Because the components of an “open” system must resist corrosion, they often are more costly than those used in “closed” systems.
“Closed” systems may use air-removal devices, expansion tanks, piping equipped with an oxygen barrier and backflow preventers. Usually, the water inside a closed system often is the same water with which it initially was filled. After the oxygen is removed, potential corrosion risks are diminished. This means less-expensive pumps, piping and components may be used.
Obviously, “open” systems in which water is intended for human use and “closed” systems are seldom mixed, because the water in a closed system is seldom fit for human use and can pose a health hazard if piped into an “open” system.
As you can see, not all components are created equal. So while that pump or valve may fit in your system, knowing whether it is better-suited for an “open” system or a “closed” system could save you money and future maintenance headaches.
As always, Wallingford Sales Co. is here (at www.WallingfordSales.com) to help you with the information and products you need in the world of commercial / institutional / industrial plumbing and washroom equipment, supplies and parts.
And remember, life is all about the flow.