Water Well Journal
Issue link: http://read.dmtmag.com/i/617280
is generally reserved for the world of larger capacity pumps for applications such as municipalities, industry, and agricul- tural irrigation, it remains a viable consideration since both types of pumps offer distinct advantages and disadvantages in the marketplace. Even though the cost for a submersible installation is usu- ally much lower than a comparable turbine, the typical service life from a vertical turbine pump is generally much longer. Typically, owner preference (i.e., bias), pump life, and cost become the deciding factors. Finally, the most common bias I have seen is the years-old argument that still exists between the various kinds of pres- sure tanks and systems. As we all know, the domestic water system was built on the reliability and low cost offered from the standard galva- nized tank. As long as the tank was either replenished regu- larly or drained and recharged with air on a periodic basis, this type of hydropneumatic tank provided reliable water storage and service for years. Then the pre-charged or bladder/diaphragm pressure tank came along and the various manufacturers of this type of tank claimed the new vessels would offer years and years of reliable service without the need to occasionally drain and recharge it. The only problem was they forgot to tell this to many of the brands that experienced premature failure of the bladder in just a few months. Given these incidents, many water system designers re- turned to using standard pressure tanks with some regular method of air recharge. Even today, many system designers elect to use constant pressure controllers on well pumps in lieu of any reserve tank. Once again, product bias is often the deciding factor. To be sure, there is no perfect product for every applica- tion. It's up to the designer and user to decide what is best for their water system. There are now more choices available not just in how to drill the well, but what you place in the well. Beyond the basic rotary technology, there are choices in sonic, air, mud, reverse, and dual wall rotary as well as stainless steel, PVC and other plastics, and mild steel for the pipe and screens. All these choices, and many more, are not usually made as much on the basis of bias, but what the experience and back- ground of the well driller knows is best for the locality, the geology, and the condition of the well. Bias in the Engineering Field As I matured both in the pump business and in consulting engineering, I witnessed various other types of bias. An example of bias I have witnessed is where quality and price clash. This is often seen in the larger water systems and engineering arenas, particularly in engineered water systems where the specifications may be somewhat loose and allowing for substitutions with possibly a lower grade of quality than the designer may have intended. Trying to become the low bidder on a project, bidding con- tractors will sometimes intentionally substitute the cost of an item of lower quality into the bid they provide to the engineer- BIAS from page 35 36 January 2016 WWJ waterwelljournal.com