A whole-house or point-of-entry (POE) water purification system can provide you with clean and healthy water throughout your home. It’s also a big investment and one that you’ll live with for the next 15 to 25 years. With that in mind, let’s explore what you should consider when choosing a system.

What’s in Your Water?

The Environmental Protection Agency (EPA) requires all U.S. water suppliers to post an annual Consumer Confidence Report (CCR). You can find the CCR for your municipal water online. If you have a well or prefer an independent assessment, you have a couple of options. You can schedule an on-site water test. Homeowners can also send a sample of their water to a water quality lab for testing.


Water filters also carry specific certifications, which you should check on your preferred models. The most important, according to the Centers for Disease Control and Prevention (CDC), is National Sanitation Foundation (NSF) certification. This certification means that the water purifier meets NSF standards for public health. You can look the product up in the NSF database. The product will also have an NSF label that indicates what the water purifier filters.

Food and Drug Administration (FDA) approval is a consideration as well. Ensure that the manufacturer makes the product with FDA-approved materials and that the filter cartridges are FDA-approved. You may also want to look for the WaterSense label. WaterSense is an EPA program through which it certifies products for water efficiency both from a consumer and environmental perspective.

Flow Rate

Flow rate is an important concern when choosing any POE plumbing system. The maximum flow rate of the water purifier, measured in gallons per minute (GPM), dictates flow throughout the entire home. If the rate isn’t high enough, you’ll experience low water pressure during periods of peak usage.

The ideal flow rate for your household is something you’ll want to discuss with your plumber. Factor in the number of residents in the home as well as the overall size of your home and the number of fixtures and appliances you might run simultaneously.

Filter Compatibility

Most POE water purification systems use filtration cartridges. Once the system has exhausted a cartridge, you simply replace it with a new one. Many systems use industry-standard sizes. This means you’re not locked into a particular brand and can shop for value. Some systems use proprietary filter cartridges. In this case, you’re at the mercy of how the brand prices its filters moving forward.

Maintenance and Notification

Consider how much maintenance a system requires. Generally, you should have a plumber inspect and clean your system annually. Your plumber can replace worn parts as needed. If a system requires additional maintenance, you’ll want to know about it upfront. Filter cartridge replacement is a given, but how will your system alert you? Most systems have an indicator light that you’ll need to check regularly. Smart systems that can send a notification to your phone are also available.

Pore Size

Pore size is a concept you may encounter often when shopping for water filters. It refers to the size of the holes that water passes through. The smaller the pore size, the better the filtration but the lower the flow rate. You might also encounter the terms absolute pore size and mean pore size. An absolute pore size of 1 micron means that no pore in the system is larger than a single micron. A mean pore size of 1 micron means that some of the pores will be larger than that but the average size of all the pores will be 1 micron.

Filter Size

Pore size and overall filter size go hand in hand. A pore size of 1 micron or less is excellent for filtration but can be restrictive to water flow. The way to counteract this is to increase the overall size of the filter. In other words, to achieve your desired filtration and flow rate, the water purifier must strike a balance between filter and pore size.

Filter Life

Factors that determine filter life are water quality and the surface area of the filter. Manufacturers typically rate their filter lifespan by gallons. A filter rated for 150,000 gallons will last the average household an entire year and a large household between six and nine months.


Prefiltration is a type of mechanical filtration that traps only the largest particles. The benefit is that it’s a relatively inexpensive filter and can extend the life of your more expensive filter media.

Particulate Filter

All water filters will have a primary particulate filter. You may see it referred to as a sediment filter. It removes dirt, sand, silt, rust, and so forth. Many experts recommend an absolute pore size of 1 micron in primary particulate filters because that size is needed to trap parasitic cysts, such as cryptosporidium.

Activated Carbon Filtration

Most POE water filters have an activated carbon filter as well. In systems without a dedicated prefilter, it may serve as the prefilter. Its main purpose is to absorb unpleasant tastes and smells. It also absorbs:

  • Chlorine
  • Herbicides
  • Pesticides
  • Chloramines
  • Pharmaceuticals
  • Trihalomethanes

UV Filtration

If you want to eliminate all pathogens from your water, you’ll need a water purifier with an ultraviolet (UV) filtration stage. UV-C is a germicidal light that neutralizes:

  • Algae
  • Viruses
  • Bacteria
  • Parasites
  • Funguses

Acid Neutralizer

If you have acidic water and want to raise its pH level, you’ll need a water purifier with an acid neutralizer. This stage will adjust pH to make your water better for cooking. It will also help minimize the corrosion in pipes and appliances that can occur due to acidic water.

Water Softening

Water hardness refers to the amount of calcium and magnesium in water. Moderate water hardness is between 3.5 and 7 grains per gallon (gpg). Hard water has 7.5 gpg or more. You can opt for a water purifier with an integrated water-softening stage. That’s usually good enough for moderate water hardness. If you have hard water, a dedicated POE water softener is typically best.

Reverse Osmosis and Remineralization

A reverse osmosis is a type of water purification and softening system. The benefit is that it removes hardness and impurities, but removing everything can be a double-edged sword. It also removes all the good minerals, so you need post-filter remineralization. The other downside is that an RO system with remineralization is typically much more expensive than a standard POE water purifier.

Your Local Water Purification Pros in Greater Denver

If you live in the Denver Metro area and would like to improve your water quality, High 5 Plumbing, Heating & Cooling is here to help. We install and service all manner of water purification and softening systems. Our plumbers pipe and repipe, perform video camera inspections, clean drains, perform plumbing maintenance and repairs, and hydro-jet. We also hook up appliances and install toilets and other fixtures, tank and tankless water heaters, sump pumps, and much more. High 5 Plumbing, Heating & Cooling also has an HVAC team that installs, maintains, and repairs all types of ducted and ductless heating and cooling systems. Contact us today with any questions or to schedule a plumbing service.

High 5 Plumbing

company icon