WATER SAMPLING AND SAMPLING STATIONS: WHO, WHAT, WHY, WHERE AND HOW
Who is required to take water samples?
All entities that are part of the water distribution chain, up to but not including the retail customer, are required to sample and test the water flowing in their systems.
Who requires the samples?
The federal government in the form of the ERA, and each state government, usually the state’s Department of Environmental Protection.
What are the requirements for water sampling?
The requirements are based on two factors:
- Customers served
- Recent experience
The range is from one sample per month for small systems, to hundreds of samples per month for larger systems. However, sampling schedule requirements escalate if recent experience detects unacceptable levels of any contaminates.
Why is water sampling performed?
The reason for sampling is to detect and prevent contamination of the nation’s water supply by any of a long list of contaminants. The Safe Drinking Water Act, also known as the SDWA, and its many amendments mandate testing for nearly a hundred chemicals and bacteria. The most commonly discussed targets of testing are lead, radionuclides, and coliform bacteria. A serious incident of coliform contamination occurred in Milwaukee in the past and highlighted the potentially fatal consequences of bacterial contamination — and of poor testing.
Where and how are samples obtained?
At each sample site, a small sample of approximately 100 ml is drawn. Prior to taking the sample, most sample takers will run water for a short time to get a fresh sample, and most will attempt some form of sterilization of the outlet nozzle — frequently using the method of “flaming” the nozzle with a small torch.
Water suppliers generally have a choice of using existing water outlets or using dedicated sampling stations. If existing outlets are used, they are most frequently:
- Existing hydrants
- Outside wall faucets
- Public drinking fountains
- Public restrooms
- Private homes or businesses
The biggest problems experienced by suppliers who use existing water outlets are:
- Restricted access caused by the weather, or by a lack of availability of a resident or other person to grant access at the specific time of day or day of the week.
- Lack of control of water as other uses of the outlets can cause unpredictability.
- Lack of reliability caused by inadvertently testing the plumbing of the sampling site, not just the supplier’s system.
- Using existing hydrants, which runs the risk of introducing drain-hole contamination, bacteria from leather seals, lead from existing hydrant components, or scaling and corrosion from the hydrant interior.
- Unreliable sterilization techniques such as “flaming” the outlet nozzle with a torch, which are frequently not welcomed by private owners and are not practical on large-nozzle existing hydrants.
Dedicated sampling stations are a superior solution to all of these issues by providing access, control, reliability, acceptance and practicality while limiting contamination.