Sampling & Monitoring

A water system monitoring plan will be different for every water system. It will depend on the water source, any specific areas of concern, type of water treatment and other infrastructure. The plan should identify what parameters need to be monitored, how often they should be monitored, and any special instructions that need to be followed to collect the samples.

Record Keeping

It is important to keep detailed records to keep track of water system performance over time. The records can also be used to demonstrate that the water being provided is safe. You should include all sampling reports and information, as well as records for your infrastructure and assets.

Checking Infrastructure

Your infrastructure and equipment need regular monitoring and this data should be recorded. This infrastructure and equipment would usually include the following:

  • source water intake/wellhead
  • treatment system (including water supply pressure gauges, inlet and outlet filter pressure gauges, the hypochlorinator pump, ultraviolet lamp, water conditioning equipment to reduce mineral content, etc.)
  • master water meter (volume)
  • flow meters (velocity)
  • valves
  • hydrants
  • reservoirs/tanks
  • water supply pumps
  • the remainder of the distribution system

From source-to-tap, you should check your system for vulnerabilities on a regular basis. At a minimum, you should include the following infrastructure-related items in your monitoring plan: 

  • New Construction Records: wells, pumps, boosters, storage tanks, water mains, disinfection equipment – recorded on an as-built drawing
  • Well Records: well drillers’ report, well log, pump suppliers’ equipment sheet, construction details of pump base, motor specifications, pump controls wiring diagrams, parts lists, etc.
  • Equipment Records: manufacturers’ specifications, operating instructions, warranty documentation 
  • Repairs and Modifications: include a drawing of the work done

Monthly Operational Record

You should have a monthly operational record at each facility in your system. Each time you visit the facility, fill out your record to indicate:

  • the purpose of the visit (e.g., routine service)
  • equipment measurements (e.g., meter readings, air level in pressure tank, water level in well before and after pumping, etc.) 
  • actions taken (e.g., lube oil added).

Sample log sheets are available at Appendix C in the Small Water System Guidebook (BC Ministry of Health). 

Sampling (Microbiological and Chemical)

The purpose of sampling is to collect a representative amount of water to be tested for various characteristics (parameters) that will provide information on the safety and operation of your water system. Samples may be collected from the water source or from various locations within the distribution system. 

the correct method of taking a sample
Figure 1: Taking a bacteriological sample from a tap. Source: Interior Health.

Many parameters are time sensitive and need to be tested within a certain amount of time after sampling. This is often called the hold-time.

Sampling is a snapshot in time. The conditions shown in today’s sample can change tomorrow, so sampling must be done regularly. Your local health authority can provide you with information on proper sampling techniques and approved laboratories. 

Chemical samples must be submitted to a laboratory that is accredited by the Canadian Association for Laboratory Accreditation (CALA) and the labs approved for microbiological testing are often also accredited by CALA. 

Depending on the parameters being sampled, a specific type of bottle or container will be required and sometimes a preservative is added to the container before sampling. An accredited analytical testing laboratory can supply the correct containers with any required preservatives and advise on hold-times. 

Microbiological, Chemical and Physical Parameters to Monitor

You will be sampling for certain microbiological, chemical and physical characteristics:

Microbiological Parameters:

The BC Drinking Water Protection Act (DWPA) requires you to take regular bacteriological samples of the drinking water in your distribution system. For small water systems 4 samples per month is required unless a different frequency is specified (in writing) by your local Drinking Water Officer (DWO).  

Microbiological Parameters


These include bacteria, viruses and protozoans. These are usually monitored by sampling and testing for indicator bacteria (coliforms). Microbiological testing will include tests for E. coli bacteria, Total Coliform bacteria and Background Colonies (bacteria).

Most water systems aim to collect one sample per week. Your DWO may also make sampling requirements conditions on your operating permit, which could specify a different sampling frequency and particular sampling locations. 

Bacteriological samples of the source water should also be collected (at least every 3 months to capture seasonal variations). These bacteriological samples will be tested for total coliform bacteria and E. coli bacteria (a type of fecal coliform bacteria). Total coliforms are found naturally in the environment and are commonly present in both surface water and groundwater at risk of containing pathogens (GARP). 

Monitoring for total coliforms at the treatment plant and in the distribution system provides information on the efficacy of your treatment system. The presence of total coliforms in water leaving any treatment plant signals that treatment has been inadequate and additional actions need to be taken (resampling, advisories, etc.).

E. coli and fecal coliform bacteria indicate recent fecal contamination from the intestines of humans and animals (mainly warm-blooded animals). The presence of E. coli or fecal coliform bacteria are a significant threat to the drinking water quality.

Chemical and Physical Parameters

The chemical and physical parameters are usually monitored by testing directly for the parameter of interest. A comprehensive chemical and physical analysis of raw water sources should be done every 3 to 5 years (depending on the type of water source). 

Chemical and Physical Parameters

 These include metals (copper, iron, lead, manganese, etc.), but also pH, antimony, arsenic, nitrate, nitrite, fluoride, selenium, sulphate, uranium, etc. Organic chemicals such as hydrocarbons, benzene, pesticides and PCBs are only tested in situations where they are suspected to be present, such as after a chemical spill. Chemical disinfection by-products (DBPs) such as trihalomethanes and haloacetic acids can also be tested. Physical parameters include temperature, colour, taste, odour, turbidity, total suspended solids, etc.

Contact your local DWO as they will have a comprehensive list of parameters that need to be tested for drinking water sources. They can also provide advice as to what chemical/physical parameters need to be tested in the distribution system (e.g., combined chlorine, disinfection by-products, turbidity, etc.). The Guidelines for Canadian Drinking Water Quality set the maximum acceptable concentrations (MACs) for chemical parameters, which will help you set up appropriate treatment procedures for your situation. This is where I’d like to put an example of a Chemical Analysis Form 

Exactly which parameters need to be monitored and how often will depend on the nature of your water system. For example, a system with a water source close to agricultural activity may need to monitor the source water for nitrates several times a year. Another example would be testing for uranium in the treated water for a water source that has an unacceptable uranium level. Testing the treated water will indicate how effective the treatment system is at reducing the uranium.

After consulting with your Drinking Water Officer (DWO), start with a baseline comprehensive chemical and physical analysis of your water source. You and your DWO can then identify a list of substances that should be routinely tested. Your DWO can provide guidance in the preparation of your water quality monitoring program. 

Monitor and Record the Data

In addition to bacteriological and chemical monitoring discussed above, you will also need to monitor and record:

  • water treatment parameters including disinfectant residuals, ultraviolet light lamp intensity (if equipped)
  • treated water turbidity
  • source/raw water turbidity
  • disinfection by-products (monitored at the extremities of the distribution system) such as trihalomethanes (THMs) and haloacetic acids (HAA5) if the water is chlorinated
  • inlet and outlet filter unit pressures
  • water consumption (daily, weekly, etc.)
  • water pressure

Representative Sampling

It is important to sample a portion of water that is as nearly identical in content and consistency as possible to the larger body of water being sampled. Most bodies of water are not well mixed; the characteristics are not the same from spot to spot. This is challenging for attempts to get a representative sample. To account for this, we take small portions of water from points across the water body or tank and mix them together into a composite sample. Proper sampling procedures are essential to obtain accurate information on the condition of your water.

Source Water Sampling:

  • Rivers: The sample(s) must represent the entire flow at that time

  • Streams: For small- or medium-sized streams, a single sampling point may be possible. Larger streams may require more than one sample.

  • Reservoirs and Lakes: In reservoirs and lakes, the water is usually poorly mixed, so a number of samples need to be collected from different depths and areas.

  • Groundwater: Groundwater also does not usually mix. Usually the only way to take a sample is from a pumped sample. If the pump has not run for some time, well pumps and casing may contribute to sample contamination, as can leaking seals and oils.

In-Plant Sampling:

Here, too, the samples need to be representative of the water passing through a particular point of the plant, not in dead zones of the reservoir. Have the sample taps/ports at points that are representative of the passing water. Follow the protocols for sampling from a tap.

Distribution System Sampling:

Sampling from the distribution system gives a true indication of the quality of water being delivered to the customer. For smaller water systems, use the customer’s faucet to collect the sample. The best sample points are front yard taps on homes supplied by short service lines, because the short service lines are located on the same side of the street as the water main. An ideal sample station has a short, direct connection with the main and is made of corrosion-resistant material.

Chlorine Residual Testing:

The free chlorine residual (tested daily) should be tested immediately after the required chlorine contact time to ensure that you are maintaining the correct CT factor before the first service connection. CT is the product of disinfectant concentration (mg/L) and contact time (minutes). Maintaining the correct CT will ensure you meet the requirements for 4 log virus removal/inactivation and 3 log protozoa removal/inactivation. For more information see the web page “Calculating CT Disinfection”. The free chlorine should also be tested at the ends of the distribution system to ensure that you are maintaining the minimum 0.2 mg/L residual throughout the entire distribution system. This is discussed in Tables 6 and 7 of the BC Small Water System Guidebook.

The total chlorine residual enables you to determine the combined chlorine residual which is the difference between the total chlorine residual and the free chlorine residual. Combined chlorine is formed when the chlorine combines with inorganic matter (e.g. iron, manganese, etc.) and organic matter (e.g. animal/human waste, decomposing vegetation, etc.). Testing the combined chlorine is particularly useful for tracking seasonal water quality changes in surface water sources and high combined chlorine may lead to the formation of disinfection by-products. Testing the combined chlorine at the ends of the distribution system may also help indicate excessive biofilm growth or intrusion/leaks in the distribution system. If you have a deep groundwater source, you may not need to test the total chlorine every day (consult your Drinking Water Officer).