Water used in homes usually comes from one of two sources: surface water or groundwater. Surface water comes from lakes, rivers, streams, and reservoirs. Groundwater comes from water stored below the ground in aquifers and wells. Knowing which source your home uses is one of the first steps in choosing the right water treatment solution.
Role/expertise: Water filtration supplier and product specialists with experience in reverse osmosis, under-sink, whole-house, UV, water softener, well water, and commercial system selection
Last reviewed: May 19, 2026
Primary sources consulted: U.S. EPA, USGS, CDC, WHO, NSF, and H2O Distributors system guides and installation resources
H2O Basics: What Does Surface Water and Groundwater Mean?
Surface water
Surface water is water found in rivers, lakes, streams, and other open bodies of water. Because it is exposed to the environment, it is more likely to come into contact with animal waste, algae, pesticides, industrial runoff, and other organic or biological contaminants.
Groundwater
Groundwater is water stored beneath the Earth’s surface. It is replenished by rainfall, melting snow, and other water that soaks into the ground. As groundwater moves through soil and rock, it can pick up calcium, magnesium, and other dissolved minerals. That is why well water and other groundwater sources are often associated with hard water and mineral-related issues.
Why Does My Water Source Matter?
Different water sources tend to require different treatment.Surface water is more likely to involve:
- microorganisms such as bacteria, Giardia, or Cryptosporidium
- organic matter
- runoff-related contamination
- disinfectants and disinfection byproducts in treated municipal water
Groundwater is more likely to involve:
- hardness minerals such as calcium and magnesium
- iron and manganese
- sulfur odor
- sediment
- acidic or low-pH water in some areas
Signs You May Have a Water Quality Problem: The H2O Basics
Water problems do not always look the same. Some are visible, some affect taste or smell, and some require testing to confirm. Here is a list of drinking water quality guidelines:
Common warning signs
- cloudy or dirty-looking water
- metallic taste
- chlorine taste or odor
- rotten egg smell
- orange, black, or blue-green staining
- scale buildup on fixtures
- dry skin or soap that does not lather well
- recurring cartridge clogging
- concern about a contaminant with no obvious taste, smell, or color
Health and Home Impacts
Some water issues are mostly nuisance problems, while others can affect health, plumbing, or appliance life.
Common home impacts
- scale buildup in pipes and water heaters
- staining on sinks, tubs, and toilets
- shorter life for appliances and fixtures
- clogged filters and reduced flow
- unpleasant taste or odor in drinking water
Possible health-related concerns
Depending on the contaminant, water quality issues may involve microorganisms, metals, chemical contaminants, or other substances that need a more targeted treatment approach. H2O Distributors already organizes educational content on contaminants, health effects, and removal methods, making this page a natural starting point before choosing a system.
How Do I Test My Tap Water?
Testing is the best way to move from guesswork to a smart treatment decision.
Start with these questions
- Is your water from a city supply or a private well?
- Are you dealing with taste, odor, staining, hardness, sediment, or health concerns?
- Is the issue visible, or do you need lab testing to identify it?
Good testing steps
- review your local water quality report if you use municipal water
- test private well water on a regular schedule
- test for the specific issue you suspect, such as hardness, iron, lead, bacteria, or PFAS
- keep the results so you can match treatment to the actual problem
- retest after installation if you want to confirm performance
Best Treatment Options by Water Problem
The right water filtration solution depends on what is actually in the water.
Common treatment approaches
- Sediment filtration for dirt, rust, sand, and suspended particles
- Carbon filtration for chlorine, taste, and odor
- Water softeners for hardness minerals
- Reverse osmosis for drinking water purification and the reduction of many dissolved contaminants
- UV sterilization for bacteria, viruses, and other microorganisms
- Specialty whole house well treatment for well-water issues such as iron, sulfur, manganese, or low pH
When Whole house vs. Under-Sink vs. RO vs. UV Makes Sense
- Makes sense when the problem affects water throughout the home
- Often the right choice for sediment, chlorine, hardness, iron, sulfur, and other issues that impact showers, laundry, fixtures, and appliances, not just drinking water
H2O Distributors offers whole house systems, water softeners, and well-water systems for these broader applications.
Under-sink systems
- Makes sense when the main goal is better drinking and cooking water at one faucet
- Often a practical option for taste, odor, and point-of-use filtration needs
H2O Distributors has a dedicated under-sink systems category.
Reverse osmosis systems
- Often the better choice when you want a higher level of drinking-water purification and broader reduction of dissolved contaminants
H2O Distributors offers reverse osmosis guides, installation resources, and support for replacement filters.
UV systems
- Makes sense when microbiological control is the concern, especially for untreated water, private wells, or situations where bacteria, viruses, or parasites may be present
- Not a catch-all solution, and prefiltration may still be needed for sediment or clarity issues
H2O Distributors sells UV systems and offers UV installation resources.
Related Solutions Sold by H2O Distributors for Water Filtration H2O Basics
How to Use Our H2O Basics Information Hub
Use this page as a starting point, then move into the sections that match your concern:
- Contaminants & Health Effects for problem-specific reading
- Water Filter Systems Guide for treatment selection
- Replacement Cartridges Guide for ongoing maintenance
- Installation & Maintenance guides for setup and service help
- Glossary if you need help with technical terms
Frequently Asked Questions on Groundwater and Surface Water
Q: What is the difference between surface water and groundwater?
A: Surface water comes from lakes, rivers, streams, and reservoirs. Groundwater comes from water stored underground in aquifers and wells.
Q: Why is groundwater often associated with hard water?
A: As groundwater moves through rock and soil, it can dissolve minerals such as calcium and magnesium, which contribute to hardness.
Q: Is surface water more likely to contain biological contamination?
A: Yes. Because it is exposed to the environment, surface water is more likely to encounter animal waste, algae, and microorganisms.
Q: When should I choose a whole house system instead of an under-sink filter?
A: Choose a whole house system when the issue affects water throughout the home. Choose an under-sink system when the main goal is cleaner water from a single tap.
Q: When does reverse osmosis make sense?
A: Reverse osmosis is a strong fit when you want more advanced drinking-water purification for a single tap or point of use.
Q: When does UV make sense?
A: UV makes sense when bacteria, viruses, or other microorganisms are the concern and the water is suitable for ultraviolet treatment.
Start with your water source, identify the actual problem, and choose the treatment system that fits your home, your water, and your long-term maintenance needs.
A boil-water advisory or boil-water order is a public health advisory or directive given by government or health authorities to consumers when a community’s drinking water is, or could be, contaminated by pathogens.
Learn how to make an emergency water filter for disaster situations out of some common items.
This method does work and can keep you heathly if clean potable water or a manufactured water filter system are unobtainable.
The Hydrologic Cycle (also called the Water Cycle) is the continuous movement of water in the air, on the surface of and below the Earth.
This cycle is the exchange of energy which influences climate. When water condenses, it releases energy and warms the environment.
90% of the garbage floating in the Earth’s oceans is plastic and less than 5% of all plastic is recycled.
The patch mostly consists of pelagic plastics, formed from plastic bags, plastic water bottles, bottle caps and styrofoam.
Hydraulic fracturing (sometimes referred to as fracking or hydrofracking) is a relatively new form of natural gas extraction.
The fluids used in the fracking process flow back to the surface, often entering the water table or polluting the drilling area, and sometimes improper disposal of waste water from the wells.
As our technology advances, so do new forms of pollution and contaminants that effect our environment and our health.
Read more about drinking water contaminants and their health effects.
Chlorine has long been recognized as an oxidative agent, meaning that it not only kills the germs in the water supply; it will damage any living tissue with which it comes in contact. And your skin, like the rest of your organs, is living tissue. But that’s not the only problem.
Since the discovery of its health benefits in the mid-1940’s, fluoride is often added to the public water supplies of industrialized countries in order to reduce the populations tooth decay, which is especially effective in low income communities, where good dental hygiene may be too costly.
Chromium-6 was found in the drinking water supply of the southern California town of Hinkley and brought to national attention by Erin Brockovich.
The EPA is reviewing effects of Chromium-6 after a recent report brought to light dangerous levels in a number of major US cities.
Giardia is a flagellated protozoan parasite that colonizes and reproduces in the small intestines of humans and other animals, which can cause giardiasis.
Symptoms of Giardiasis usually show after 3 to 4 days, and include gastrointestinal and constitutional problems.
Cryptosporidiosis is a disease caused by the parasite Cryptosporidium parvum.
Since a outbreak in 1993 in Wisconson, new attention has been focused on determining and reducing the risk for Cryptosporidiosis from community and municipal water supplies.
What is reverse osmosis? What is a 4-Stage system? What are the components in a system? Visit our ‘How Reverse Osmosis Works‘ guide to find the answers.
Also see out list of contaminants RO removes and comparison chart for particle sizes to learn more about reverse osmosis.
What is ultraviolet light? Do I need to filter the water before the UV process? How exactly can light kill organisms?
Visit our ‘How Ultraviolet Purification Works‘ guide to find out how it works.
The typical water softener is a mechanical appliance that’s plumbed into your home’s water supply system. All water softeners use the same operating principle: They trade the minerals for something else, in most cases sodium. The process is called ion exchange. More…
Step by step instructions on installing replacement cartridges and sanitizing filter housings. It is highly recommended that you clean and sanitize your system once a year.
Need help installing your new RO system, how to perform maintenance, or how often to change your cartridges?
View our printable Reverse Osmosis Installation Guide to learn more.
Step by step instructions on making a connection with Quick-Connect fittings. Quick-connect fittings allow you to connect and disconnect tubing without the need of tools. For larger, plumbing size fittings read our using twist lock guide.
Step by step instructions on making a connection with Twist and Lock fittings. Twist-Lock fittings allow you to connect and disconnect tubing without the need of tools.
Step by step instructions on making a connection with SharkBite Push-To-Connect fittings. SharkBite fittings allow you to connect and disconnect pipes without the need of using PVC glue or welding copper.
Need to filter water but not sure about the differences between or applications of our systems?
Use our Water Filter Systems Guide to find out which system is best for your filtration needs.
Need to replace your system’s cartridges but not sure what type is best for your system?
View our Cartridge Replacement Guide or contact us to find out what you need.
View a chart comparing the specifications of all the reverse osmosis systems we sell on this site. All bladder tanks are NSF certified.
The size of your water softener depeneds on the total grain per day that need to be removed.
This is determined by the number of people in your household, grain per gallon (GPG) hardness and the amount of Iron present in the water.
A micron is a unit of measurement for how small of particles a filter will catch. The lower the micron size, the tinier the ‘holes’ in the filter cartridge are that allows water to pass through, ranging from 0.1 absolute to 150 microns.
Use our Pore Size Efficiency Guide to find out what micron size to use.
Pleated sediment cartridges remove dirt, rust and sediment from water while providing an increased surface area and longer life. Pleated filters down to 5 microns are washable and reusable.
Use our Pleated Sediment Cartridge Comparison to find the filter cartridge you need.
Aquariums need three types of filtration to maintain a healthy environment for freshwater, saltwater or amphibian aquariums (sediment filtration, carbon filtration, and removal of biological contaminants).
When traveling around the state or the country in a RV you might not always know where you will be getting the water from or what might be in it. Water that is stored in a RV holding tank will not stay potable for long and can become a breeding ground for algae and bacteria.
Chemicals added to public water supplies, like chlorine, can be harmful to the living cells of plants.
When brewing beer with tap or bottled water, chlorine and chloramine present in the water can combine with malt phenols in the wort to create a compound called chlorophenol, which can give the beer a medicinal taste.
View our Filtered Water for Home Beer Brewing guide.
Bottled water requires a lot of resources to manufacture and ship, and costs a lot more than reverse osmosis water.
Use our Bottled Water Cost Calculator to find out how much of an impact you have on the environment.
Reverse osmosis systems can remove contaminants that are unhealthy and possibly deadly through a combination of granular activated carbon, carbon block & sediment filtration, and thin film membranes.
Chart displaying the sizes of well-known objects and particulates, illustrated in the size of the micrometer (micron).
View the comparison chart for particle size removal of thin-film membranes used in reverse osmosis systems.
A chart of RO Membrane performance over a range of temperatures and pressures. Membranes are tested at 65 PSI of pressure and temperature of 77 degrees.
Change in either variable affects membrane performance changes accordingly. Higher pressures increase production and vice versa.
Hard water is the most common problem found in the average home. Hard water is water that contains dissolved hardness minerals above 1 GPG, such as calcium, magnesium and lime.
Water softening fixes this problem without adding any chemicals into your water supply.
Hard water is not as efficient as soft water for bathing, washing dishes, clothes, car & many other uses.
See Also:
Hard Water and Laundering
Water Hardness in the US
Water hardness can affect showering and laundering by making soaps and detergents less effective and leaves a film on your skin.
Find out if you live in an area with slight or very hard water by looking at our hard water map of the United States.
