A: A PVC well screen is something that a water well driller is going to use at the very bottom of the well.
Usually, it’s capped or plugged at the very end and that is the piece of pipe with slots cut all the way up in it. The slots can be from 6 thousandths of an inch to 40 thousandths of an inch.
This allows the water from that water-bearing sand to flow up into the casing and then be pumped wherever it needs to go out of the well.
Water is a precious resource that while in some parts of the world seems unlimited, in other areas it’s harder to find. Often, especially in rural areas with no municipal water system, access to water is usually found underground. Specifically, in natural reservoirs beneath the earth called aquifers.
So, how do you extract that water and distribute it for your needs? You have to dig—a well that is. A well is basically a hole drilled beneath the ground to access the water in an aquifer below.
It takes the deployment of a pipe and a pump to draw the water from the aquifer up to the surface. However, there’s more to it than that such as a well screen that filters out unwanted sand and particles of rock and earth. Those particles can clog the pipe and render the well useless.
Wells can be built in various shapes and sizes and it’s determined by the ground it’s drilled into, and the volume of water being pumped. You might think well use is rare in the U.S., with so many developed metropolitan areas. However, over 40 million people in the USA alone depend on wells as the primary water supply for their homes and families.
Types Of Wells
- Bored/Shallow wells are typically drilled into a water source that is unconfined and usually 100 feet deep or less.
- Consolidated Wells are bored into a natural rock formation that is no dirt and won’t collapse. These are usually found around 250-300 feet below the surface on average.
- Unconsolidated Wells are drilled through a formation that is made up mostly of soil, clay, sand, and other material that is collapsible onto itself.
Well Construction
The construction of a private well is centered on determining the right location for the well, correctly sizing the system and proper construction method.
It’s best to hire a professional well construction contractor as they are experts in hydrology in the area they serve. Not to mention, they will be certified so they’ll know the local codes and regulations before building. Constructing a well properly is the foundation for a long-lasting and easily maintained well.
A well is made up of quite a few components, but the core materials and components include:
- Casing— Used to maintain the hole in the earth while not allowing it to collapse into the well. The most common casings are PVC pipe, galvanized steel, black steel, and concrete pipe.
- Grout— Is a sealant that fills the gaps around the exterior of the well. It protects it against contaminants and is often made of cement, concrete, or bentonite.
- Well Screen— A filtration device that keeps gravel and sand from getting in the well while still allowing the passage of water in. Screens are made from many different materials, the most popular being PVC pipe that is slotted.
- Gravel pack— Is packed around the well screen to keep sand from entering the well. It is essentially like a sieve that complements the screen and further assists in filtration. However, it also adds stability to the well.
Filtration Is Crucial
A well screen is a critical component of any water well and helps maintain its efficiency and increase longevity. That is because a well screen is simply a device that filters out sediment in the intake portion of a well in an aquifer. Some wells are in consolidated aquifers and others in non-consolidated ones, but all wells need a well screen.
The well screen has more than one task besides filtering, however. All in all a well screen:
- Is critical for steady water flow
- Keeps sediment out of the well
- Can be built using different materials
The role that a solidly built well screen plays in the function of a well is immeasurable when discussing efficiency and cost of ownership. Regardless of what material the well screen is made from, they all serve the same purpose.
However, a well screen can be as primitive as a hand-made contraption or a sophisticated, precisely engineered, high-efficiency screen. The higher the quality of the screen, the longer the well will last without failing.
What Makes A Quality Well Screen?
Since well screens can be made to varying degrees of quality, it’s important to know what the criteria are for a high-quality screen. A well screen that is considered to be top-tier and well manufactured will have to meet certain design criteria and function to certain standards.
Criteria:
- A large open area
- Slots that don’t clog
- Corrosion-resistant
- Sturdy column and collapse strength
Functional Criteria:
- Easily manufactured
- Low tendency to develop sediment build-up
- Low head loss
- Able to control sand pumping no matter the type of aquifer
Slot Size & Sieve Analysis
Selecting the proper well screen slot size is a major step to ensure you get maximum performance from the well. Typically, the screen should be designed to withhold half of the formation. Proper velocity is critical as you should not exceed 1/10 of a foot per second. You get the proper velocity by dividing the GPM of the well yield by the open area of the screen in square inches.
As far as getting the right slot size, you need to perform a size analysis of your formation samples. Looking at the grain sizes of the samples taken, you can draw a grain-size distribution curve. You can use many methods to get the information needed on grain-size distribution.
The most commonly used method includes processing the sample materials through a stacked series of metal sieves. During this process, each sieve filters out a specific percentage gradually getting finer on the way down. The finest material is left at the bottom and the sieve analysis is what determines the slot size, but also other design considerations.
We Have The PVC Screen You Need
At Gulf Coast Pump & Supply, we can guarantee that we have the PVC well screens you need. That’s because we have our custom fabrication shop right on site. Any size, diameter, and unique designs you need, we can build.
Contact us today for all your water well screen needs!