Water filtration can feel overwhelming—but it doesn’t have to be. Whether you're dealing with sediment, strange odors, or just want better-tasting water, understanding the basics is the first step to making the right choice. In this article we will cover what water filtration is and the best way to select a filtration system for your needs.
What Is Water Filtration?
Water filtration is the process of removing unwanted particulate and undesirable taste and odors. It is important to understand that traditional water filters are not water treatment systems. You must always get your water properly tested before determining which filtration system to use.
WARNING: Do not use with water that is microbiologically unsafe or of unknown quality without adequate disinfection before or after the filter. Traditional filters improve appearance, taste, and odor—but they do not make unsafe water safe.
Filtration systems typically remove:
- Sediment (sand, silt, dirt, scale, rust)
- Undesirable taste and odor
- Certain nuisance compounds such as Radon and Volatile Organic Compounds (VOCs)
How to Properly Select a Water Filter
Selecting a water filter correctly is critical. The most common mistake is choosing a filter housing first and then trying to fit a cartridge into it. This often leads to:
- Insufficient flow capacity
- Reduced cartridge lifespan and frequent cartridge changes
- Higher overall filtration costs
When it comes to traditional sediment filter housings and cartridges, it is better to err on the side of too large than too small. Here are the Five Required Steps:
Step 1 – Have Your Water Tested
Before selecting any filtration system:
- Ensure your water is microbiologically safe for drinking and cooking
- Identify specific water quality issues
- Determine particulate size
Testing helps determine what type of cartridge is required and ensures proper system sizing.
Step 2 – Determine the Type of Filter Cartridge Required
The type of cartridge needed depends on the specific water issue:
► Sediment / Appearance Issues
Use Sediment cartridges such as:
- Spun Polypropylene (SP)
- Pleated Polyester (PPE)
- String Wound (SWP, SWBC)
► Taste Issues
Use Activated Carbon cartridges:
- Carbon Block (CB)
- Granular Activated Carbon (GAC)
- Carbon Wrap (CW)
► Odor Issues
Also use Activated Carbon cartridges (CB, GAC, CW).
Step 3 – Verify the Desired Flow Rate (GPM)
Desired Flow Rate is the volume of water in gallons per minute (GPM) that you want to have available when multiple faucets or appliances are in use. To determine the flow requirement needed for your filter, rather than basing this need on the gallons per day usage of your home, you would need to calculate your peak flow demand in gallons per minute (GPM). Below is a guide on the GPM range of common appliances and fixtures.
Typical Fixture GPM Ranges:
- Dishwasher: 2–3 GPM
- Washing Machine: 4–5 GPM
- Bathtub: 3–8 GPM
- Shower: 2–5 GPM
- Faucet: 2–3 GPM
- Toilet: 2.5–5 GPM
Consider:
- Simultaneous appliance use
- Lawn/garden watering
- Future renovations (additional bathrooms, laundry)
Step 4 – Select Cartridge Size
Choose a cartridge with a flow capacity significantly higher than your required GPM.
Rule of Thumb:
- Minimum: 1.5× desired flow, Light sediment load: 1.5× may suffice
- Recommended: 2x desired flow
- Heavy sediment load: up to 3x desired flow
Why Oversize?
Published flow rates are based on clean cartridges. As sediment accumulates pressure drops and flow decreases.
If you select a filter cartridge at the minimum desired flow rate, the cartridge will quickly fall below acceptable performance and require premature replacement resulting in increased filtration costs.Ideally, cartridges should last 4–6 months, with changeout at six months to prevent bacterial buildup.
Cartridge Size Options
Outside Diameter:
- Standard: 2½"–2¾"
- Giant: 4½"
Length (available in both Standard and Giant size Outside Diameter):
- 10" Nominal
- 20" Double Length
Notes:
- Overlap may exist between 20" Standard and 10" Giant options.
- Flow restriction is typically caused by piping and filters—not municipal supply.
- Upgrading housing size can resolve flow limitations.
Step 5 – Select the Filter Housing (Last Step)
The housing must accommodate the correctly sized cartridge.
Housing Types:
- Slim Line
- Standard
- Valve-In-Head (VIH)
- Giant
- Stainless Steel
- High Temperature
Material Options:
- Polypropylene
- Polypropylene / Styrene-Acrylonitrile
- Polypropylene / Styrene-Acrylonitrile with Stainless Steel Thread Inserts
- Stainless Steel
- Glass-Reinforced Nylon (High-Temp)
Bowl Options:
- Clear (5-year lifespan) must not be used indirect sunlight
- Blue (10-year lifespan) suitable for use where there is UV exposure
- Red (High-Temp) suitable for use where there is UV exposure
- Stainless Steel (High-Temp, High Pressure) suitable for use where there is UV exposure
Other than the filter bowl lifespan, temperature rating, and UV limitations, the choice between blue and clear filter bowls often come down to customer preference. Some customers like to see what is going on inside their filter bowl, other customers prefer not too.
Giant housings offer multiple inlet/outlet connection sizes.
To help decide between these, consider Flow Velocity. It is recommended to size piping to maintain a water velocity of 5 ft/second (1.524 LPM). Five feet per second is a threshold that is widely accepted by engineers and designers because beyond this velocity, the friction losses, danger of water hammer, and pipe movement due to water momentum changes are deemed to be too high.
- 3/4” connections should be limited to 7 GPM
- 1” connections should be limited to 12 GPM
- 1-1/2” connections should be limited to 27.5 GPM
When higher flow capacity is required, it may be necessary to install 2 filter housings in parallel.
In Conclusion:
In conclusion, choosing the right water filtration system doesn’t have to be complicated—it just requires a thoughtful, informed approach. By understanding what filtration can and cannot do, starting with proper water testing, and carefully matching the right cartridge, flow rate, and sizing to your specific needs, you can avoid common mistakes and unnecessary costs. Taking the time to size your system correctly and prioritize performance over convenience ensures not only better water quality but also longer-lasting, more efficient filtration. Ultimately, a well-chosen system provides peace of mind—delivering cleaner, better-tasting water for your home while protecting your investment in the long run.
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