First, it makes it difficult to determine when a well requires maintenance in order to avoid rehabilitation. Losses in specific capacity over time can be nonlinear, and this behavior has negative consequences. A decrease in specific capacity is an indication of well fouling however, by the time large losses in specific capacity are observed, well plugging has progressed to the point where rehabilitation, rather than maintenance, is required to restore lost capacity. Specific capacity is a measure of well performance (Q/s) indicating the amount of water that is available per unit drawdown. Wells are often pumped at variable discharge rates, which vary with drawdown, and drawdown increases with the duration of pumping. Optimization of design results in a well that minimizes drawdown and construction costs while meeting the required discharge rates and intervals. If you try to discharge more water than can be supplied by the aquifer, or that will pass the aquifer-well connection, water levels in the well decrease until the pump is exposed and the well runs dry.ĭrawdown is reduced by the construction of more efficient wells. The pumping water level is called drawdown (s), and the greater the drawdown, the higher the power costs. This is often referred to as specific capacity, the vertical distance between the static, non-pumping water level. There are several quantitative measures of well performance, the most common being discharge (Q), the volume of water produced per unit time. If you have more questions about tank volume and Wessels products, feel free to reach out by chatting with us in the chat window at the bottom right of our website, by emailing us at, or by calling our offices at 31.Neil Mansuy is vice president of technical services for Subsurface Technologies, Inc. A fixed-diaphragm tank like the NTA, however, lists both the tank volume and the maximum acceptance volume. For example, in a Wessels Company NLA series tank, the total volume of the tank is also the number of gallons the tank can hold, making the tank a full acceptance volume tank. If the chart says tank volume, that means the usable volume inside the tank is the total volume of the tank. You can tell if a tank is a full acceptance tank by looking at its chart either online, on the submittal, or in the literature for each style of tank. Fixed-diaphragm tanks are not full acceptance tanks because the diaphragm is confined to only a portion of the tank. As a standard, Wessels Company offers tanks pre-charged to 40 PSI, which can easily be adjusted and reduced in the field to fit the pressure needed within the system.Īll replaceable bladder tanks Wessels offers are considered a full volume acceptance tanks, since the bladder inside can fully expand within the tank, allowing all the available space inside the tank to be used. (pressure in the tank should be set accordingly: 10% below pump cut-in pressure (hydropneumatics) equal to pressure reducing valve pressure (hydronic), equal to line pressure (thermal – domestic water heater protection). However, the tank should be charged on the tank’s air side to the minimum pressure needed within the system and filled to the maximum pressure in water required to adjust the tank’s pressure correctly. The volume of water in a tank, called the acceptance volume, is sometimes expressed as a decimal or percentage against overall tank volume, called an acceptance factor. In real-world plumbing systems, the tank should not start at the maximum pressure and the air cushion pressure should not fall to zero. Maximum Acceptance Volume: The maximum amount of fluid inside the tank before stretching the bladder/diaphragm.Īcceptance Factor: The percentage of of tank volume storing fluid, expressed as a decimal.ĭrawdown Volume: The amount of water that is drawn out from a starting tank pressure down to the minimum pressure.Ī tank’s drawdown volume is the amount of water that is stored between a high and low pressure, which is usually determined by a pump switch. Tank Volume: The overall volume of the tank, including air and water.Īcceptance Volume: The amount of water inside the tank. 4 years ago News and Events acceptance, draw down, technical, volume
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