How To Read Your Water Test Results

Getting your water tested is an important step in the process of determining the proper water treatment equipment to buy. Water test results from accredited laboratories are usually very thorough, but this can make them a little confusing to read. In this article, we show you some typical laboratory water test results and where to find the relevant bits and pieces of information.

The water test results that you receive back from a laboratory are really the results of many individual tests that are presented in a unified report. As an example, pH is a single test, as is sodium. The result of each of these tests will be given it's own line on the report like this:

Water Test Line Items

Each column in the report will give you different information about that particular water test line item. Some columns are more important than others:

Water Test Results Column Meaning

Date and Time Columns:  these are important for the lab for their quality assurance processes but really not very valuable for the person reading the test results

MAC - Maximum Allowable Concentration:  this is a super important column to notice and understand. For water contaminants that are dangerous, Health Canada sets a maximum allowable level for drinking water. If your water exceeds this limit then your water is not safe to drink.

AO - Aesthetic Objective:  some contaminants aren't dangerous but make the water undesirable to use. Examples are compounds that create a taste, colour, or odour in the water. For these contaminants, Health Canada produces an Aesthetic Objective. If the contaminant is below this level it likely won't cause any annoying issues with your water.

Results:  strangely it can be quite hard to pick out the actual results on a water test. This column can be given all kinds of different names depending on the lab used. Most often it will be called 'results' but as you can see from the example shown it may be called something completely different. If you have any doubt about which column is the results column it's often useful to use the pH results line to figure this out. The "aesthetic" or "suggested" pH value will be shown as a range while the actual result will be shown as a single number.

Units:  some water tests will have a separate column for units while other test results will incorporate the units into another column. It's very important to know the units that your water test is reported in. As it relates to sizing water treatment equipment, the standard units used are as follows:

  • hardness = mg/L or Grains per Gallon (GPG)
  • iron = mg/L or PPM
  • manganese = mg/L or PPM
  • pH = no units for pH

If you're going to be using your water test results in a water softener sizing tool or another similar sizing equation it's critically important that the units you use match the units that the tool is expecting. Here's what the units you see in a report actually mean:

  • mg/L = milligrams per litre
  • ug/L = micrograms per litre
  • ppm = parts per million
  • ppb = parts per billion
  • gpg = grains per gallon

Some of these units can be interchanged with one another:

  • mg/L = ppm
  • ug/L = ppb

Knowing how to convert from one to the other can be very useful:

  • to convert from ug/L or ppb to mg/L or ppm divide by 1000
  • to convert Total Hardness expressed as mg/L to Grains per Gallon divide by 17.1

So now that you know how to read your water test results, the next step is knowing what to look for. If you're using the results to choose water treatment equipment there are a few different test results you need to find and highlight on the report. These are Total Hardness, Iron (Fe), Manganese (Mn), and pH.

However, it's also very important that you find any results that exceed the MAC (maximum allowable contaminant) level and make sure these are addressed by any water treatment equipment you decide to purchase.