What Should You Test Your Catchment or Well Water For on the Big Island?
If your Big Island home gets its water from a rainwater catchment tank or private well, you may have wondered whether you should have the water tested.
But before ordering a water test, there is a more useful question:
What are you actually trying to find out?
Are you concerned that the water could make you sick?
Does it taste strange?
Does it smell bad?
Are you seeing staining or sediment?
Are you buying a home and need professional laboratory results?
And just as importantly, does the property use rainwater catchment or a private well?
Catchment water and well water have different potential sources of contamination, so we use different testing panels for each type of water supply.
Water That Tastes Good Isn’t Necessarily Safe
One of the biggest misconceptions about drinking water is that you can tell whether something is wrong by looking at it, smelling it or tasting it.
Sometimes you can.
High mineral levels, corrosion and other water-quality problems can produce noticeable symptoms such as:
- Metallic taste
- Rotten-egg odor
- Cloudiness
- Orange or reddish staining
- Blue-green staining
- Scale or mineral deposits
- Salty or unusual taste
The U.S. Environmental Protection Agency has established secondary drinking-water guidelines for several substances and characteristics that primarily affect things such as taste, odor, staining, corrosion and mineral deposits. EPA Secondary Drinking Water Standards
But some of the contaminants that matter most from a health standpoint may produce no obvious taste, smell or appearance at all.
That is why it helps to separate water testing into two basic questions:
Is the water potentially unsafe?
and
Is there something affecting the taste, smell, appearance or plumbing?
Sometimes the same test helps answer both questions. Other times it doesn’t.
Catchment Water and Well Water Are Different
Rainwater catchment and private wells are both private water sources, but the water reaches your house in very different ways.
With a catchment system, the path generally looks something like this:
Rain → Roof → Gutters → Catchment Tank → Pump → Filtration/Treatment → Plumbing → Faucet
Potential contamination can enter through the roof, animals, leaves, gutters, storage tank, sediment, treatment equipment or plumbing.
The Hawaiʻi Department of Health recommends that residential rainwater catchment systems be properly designed, regularly maintained and periodically tested. Hawaiʻi Department of Health Rainwater Catchment Guidance
With a private well, the water comes from groundwater.
Possible concerns can include bacteria as well as naturally occurring minerals, groundwater contamination, nearby septic or wastewater systems, fertilizers and, in some locations, higher concentrations of dissolved minerals or salts.
Hawaiʻi DOH advises owners of private wells not to assume their well water is safe simply because it comes from underground. Regular bacteriological and chemical testing is recommended. Hawaiʻi Department of Health Private Water Wells Guidance
Because the potential risks are different, we do not use the same laboratory panel for catchment water and well water.
What We Test for in Big Island Catchment Water
Our catchment water testing includes:
- Total Coliform
- E. coli
- Turbidity
- Copper
- Lead
The Hawaiʻi Department of Health’s residential rainwater catchment screening guidance includes E. coli, turbidity, lead and copper. Our testing also includes Total Coliform as an additional indicator of possible contamination.
Total Coliform: Is Contamination Getting Into the System?
Total Coliform is a group of bacteria commonly found in soil, vegetation and the environment.
Finding Total Coliform does not automatically mean that dangerous fecal bacteria are present. Instead, it acts as an indicator that contamination may be entering the water system somewhere.
For a catchment system, possible sources could include:
- Debris on the roof
- Dirty gutters
- Birds or rodents
- Organic material entering the tank
- Tank contamination
- Poorly maintained filters
- Household plumbing
Our reference level is:
Absent in 100 mL
A positive result means the system should be investigated rather than simply assuming the water is fine because it looks and tastes normal.
E. coli: A More Serious Bacterial Concern
E. coli is different.
Its presence can indicate contamination from human or animal fecal material and represents a potentially serious health concern.
This is particularly relevant to rainwater catchment systems because the roof is part of the water collection system. Birds, rats and other animals can contaminate the collection surface before the water ever reaches the tank.
The Hawaiʻi catchment screening reference is:
Absent in 100 mL
In other words, E. coli should not be detected.
If E. coli is found, the source of contamination needs to be addressed before assuming the water is suitable for drinking.
Turbidity: How Clear Is the Water?
Turbidity measures the amount of suspended material in the water.
For catchment water, the Hawaiʻi DOH screening reference is:
Less than 5 NTU
NTU stands for Nephelometric Turbidity Units.
Higher turbidity can indicate sediment, debris or other suspended material. More importantly, very cloudy water can interfere with treatment and disinfection.
For example, ultraviolet treatment works best when the water reaching the UV system is sufficiently clear. Suspended material can interfere with effective treatment.
So turbidity isn’t simply about whether the water looks attractive in a glass. It can also provide useful information about the catchment and filtration system.
Lead: You Cannot Judge It by Taste or Appearance
Lead is one of the best examples of why water shouldn’t be judged by taste alone.
Lead in drinking water generally does not provide a taste, smell or visible warning that it is present.
Lead can enter drinking water through plumbing components and corrosion rather than necessarily coming from the original water source itself.
For Hawaiʻi’s residential catchment screening test, the reference level is:
0.010 mg/L or less
That is equivalent to 10 parts per billion (ppb).
Lead exposure is a health concern, particularly for children and during pregnancy.
The EPA provides additional information on lead and copper in drinking water and how plumbing materials can contribute these metals to water. EPA Lead and Copper Rule Information
Copper: Plumbing and Water Quality Can Interact
Copper can also enter water through household plumbing.
The catchment screening reference level is:
1.3 mg/L or less
Unlike lead, elevated copper or corrosive water may occasionally give you clues.
Possible signs include:
- Metallic taste
- Blue-green staining
- Plumbing corrosion
But laboratory testing is the appropriate way to determine the actual copper concentration.
What We Test for in Big Island Well Water
Private wells require a different testing panel.
Our well water testing includes:
- Total Coliform
- E. coli
- Nitrate as Nitrogen
- Nitrite as Nitrogen
- Combined Nitrate and Nitrite as Nitrogen
- pH
- Total Dissolved Solids (TDS)
These parameters help answer different questions about groundwater quality.
Total Coliform and E. coli in Well Water
Just as with catchment water, bacteria are an important concern with private wells.
For Total Coliform, the reference is:
Absent in 100 mL
Its presence can indicate possible contamination or a problem with the well or plumbing system.
For E. coli, the reference is also:
Absent in 100 mL
Finding E. coli is more serious because it may indicate fecal contamination.
Potential contamination sources around a private well can include problems with the well itself, wastewater, septic systems or contaminated groundwater.
Nitrate: An Important Groundwater Test
Nitrate testing is especially useful for private wells because nitrate can enter groundwater from sources such as:
- Fertilizers
- Septic systems
- Wastewater
- Agricultural activity
- Natural deposits
The drinking-water reference level for nitrate, measured as nitrogen, is:
10 mg/L or less
High nitrate concentrations are particularly dangerous for infants because they can interfere with the blood’s ability to carry oxygen.
You generally cannot determine whether nitrate is present by tasting or looking at the water.
EPA identifies nitrate as one of the regulated inorganic drinking-water contaminants and sets the maximum contaminant level for nitrate, measured as nitrogen, at 10 mg/L. EPA National Primary Drinking Water Regulations
Nitrite
Nitrite is chemically related to nitrate and can also indicate groundwater contamination.
The reference level, measured as nitrogen, is:
1 mg/L or less
Like nitrate, elevated nitrite is particularly concerning for infants.
Combined Nitrate and Nitrite
We also test the combined concentration of nitrate and nitrite.
The reference level is:
10 mg/L or less, measured as nitrogen
This provides another way of evaluating the overall nitrate and nitrite concentration in the water.
pH: Is Your Well Water Acidic or Alkaline?
pH tells us how acidic or alkaline the water is.
The EPA secondary guideline is:
6.5 to 8.5
This is primarily a water-quality and plumbing guideline rather than a health-based maximum contaminant level.
Low-pH water can be more corrosive. That matters because corrosive water can contribute to metals entering the water from pipes and plumbing fixtures.
Higher-pH water may contribute to:
- Slippery-feeling water
- Unusual taste
- Mineral deposits
EPA includes pH among its secondary drinking-water standards, which address aesthetic and technical issues such as taste, corrosion, staining and deposits. EPA Secondary Drinking Water Standards
Total Dissolved Solids: What’s Dissolved in the Water?
Total Dissolved Solids, usually abbreviated TDS, measures the overall amount of dissolved substances in water.
The EPA secondary guideline is:
500 mg/L or less
TDS can include dissolved minerals and salts.
Higher TDS may contribute to:
- Salty or mineral taste
- Deposits
- Staining
- Scale buildup
In some coastal groundwater situations, elevated dissolved solids can also be one clue that saltwater may be influencing the water supply.
TDS does not tell you exactly which minerals are present. Instead, it provides a useful overall measurement of how much dissolved material is in the water.
Catchment vs. Well Water Testing at a Glance
| Parameter | Catchment Test | Well Test |
|---|---|---|
| Total Coliform | Yes | Yes |
| E. coli | Yes | Yes |
| Turbidity | Yes | No |
| Lead | Yes | No |
| Copper | Yes | No |
| Nitrate | No | Yes |
| Nitrite | No | Yes |
| Combined Nitrate/Nitrite | No | Yes |
| pH | No | Yes |
| Total Dissolved Solids | No | Yes |
The important point is that one water test does not answer every possible water-quality question.
The source of the water and the reason for testing determine which tests make sense.
Are You Testing for Health or for Taste?
This is probably the most important distinction for homeowners.
Someone may contact us because the water:
- Tastes metallic
- Smells like rotten eggs
- Leaves orange stains
- Leaves blue-green stains
- Looks cloudy
- Leaves mineral deposits
Those are legitimate water-quality concerns, but they don’t necessarily require the same tests used to evaluate common health-related contaminants.
For example, the EPA associates iron with rusty coloration, sediment, metallic taste and reddish or orange staining. It associates elevated copper with metallic taste and blue-green staining. High TDS can contribute to deposits and salty taste.
These are examples of what EPA calls secondary drinking-water concerns. EPA Guidance for Taste, Odor, Staining and Other Secondary Water Issues
What If My Water Smells Like Rotten Eggs?
A rotten-egg smell is commonly associated with sulfur-related compounds.
Neither our standard catchment panel nor our standard well panel is specifically a sulfur test.
Likewise, if your primary concern is orange staining, hardness or another specific taste, odor or mineral issue, additional or different testing may be appropriate.
That’s why it is useful to tell us why you want the water tested, rather than simply requesting a generic water test.
What If My Water Looks and Tastes Perfect?
This is the opposite problem.
Water can be crystal clear, have no objectionable odor and taste completely normal while still containing something you would want to know about.
Examples can include:
- E. coli
- Nitrate
- Nitrite
- Lead
You cannot rely on taste, odor or appearance as a substitute for laboratory testing.
When Should Catchment Water Be Tested?
You may want to test catchment water when:
- You are buying a home
- A lender requests laboratory water results
- You don’t know when the water was last tested
- The catchment system has had maintenance or repairs
- The tank has recently been cleaned
- You have had a problem with filtration or UV treatment
- You are concerned about bacterial contamination
- You want to check for lead or copper
- You simply want a baseline for the water coming from your home
Hawaiʻi DOH recommends that catchment systems be properly designed, regularly maintained and periodically tested.
When Should Well Water Be Tested?
Hawaiʻi DOH specifically warns private well owners that they should not assume their water is safe for consumption.
The state’s private-well guidance recommends regular testing for bacteriological and chemical contaminants and notes that private wells serving individual residences are not regulated in the same manner as public water systems. Read Hawaiʻi DOH’s Private Water Wells Guidance
Well testing may be particularly worthwhile when:
- You are purchasing a property
- Testing has not been performed recently
- There is nearby agricultural activity
- Septic systems or wastewater sources are nearby
- The well has been repaired or modified
- The water’s taste or appearance has changed
- You want a baseline of the well’s water quality
With a private residential well, monitoring the water quality is ultimately the property owner’s responsibility.
Buying a Big Island Home With Catchment or Well Water?
Water testing frequently comes up during real estate transactions on Hawaiʻi Island.
A buyer may simply want to understand the property’s water quality, or a lender may require professional testing and documentation.
That is different from using a home test kit.
We professionally collect the water sample at the property and submit it to a laboratory for analysis.
If testing is being performed for a real estate loan, you should confirm the specific testing requirements with your lender because requirements can vary depending on the loan program and property.
So What Should You Test Your Water For?
Start with the source.
If You Have a Catchment Tank
Our catchment panel tests:
Total Coliform, E. coli, Turbidity, Copper and Lead
These tests help identify bacterial contamination, water clarity issues and metals that may enter drinking water.
If You Have a Private Well
Our well panel tests:
Total Coliform, E. coli, Nitrate, Nitrite, Combined Nitrate/Nitrite, pH and Total Dissolved Solids
These tests help identify bacterial contamination, certain groundwater contamination risks and characteristics that can affect water quality, taste and plumbing.
And if the reason you’re testing is something specific such as sulfur odor, iron staining or hardness, you may need a different type of water analysis.
That’s why the best place to start isn’t simply:
“Can you test my water?”
It’s:
“What am I trying to find out about my water?”
Big Island Catchment and Well Water Testing
Big Island Home Inspectors provides professional water sample collection for rainwater catchment systems and private wells on Hawaiʻi Island.
We no longer provide general home inspections. Our focus is water-quality testing.
If you need testing for a real estate transaction, lender requirement or simply want more information about the quality of your home’s private water supply, book now to schedule testing.
Catchment water testing and well water testing use different laboratory panels, so let us know which type of water system the property has when scheduling.
References & Further Reading
The following government resources provide additional information about private water supplies and drinking-water quality:
Hawaiʻi Department of Health, Safe Drinking Water Branch: Rainwater Catchment
Information for Hawaiʻi homeowners about the design, maintenance and periodic testing of residential rainwater catchment systems.
Hawaiʻi DOH Rainwater Catchment Guidance
Hawaiʻi Department of Health, Safe Drinking Water Branch: Private Water Wells
Guidance for owners of private residential wells, including testing recommendations and potential sources of groundwater contamination.
Hawaiʻi DOH Private Water Wells Guidance
U.S. Environmental Protection Agency: National Primary Drinking Water Regulations
Federal health-based drinking-water standards for contaminants including nitrate and nitrite.
EPA National Primary Drinking Water Regulations
U.S. Environmental Protection Agency: Secondary Drinking Water Standards
Guidance addressing pH, TDS, iron, taste, odor, staining, corrosion and other primarily aesthetic or technical water-quality concerns.
EPA Secondary Drinking Water Standards
U.S. Environmental Protection Agency: Lead and Copper Rule
Background information about lead and copper in drinking water and the role household plumbing and corrosion can play.
EPA Lead and Copper Rule