THMdw

Trihalomethanes  – Drinking Water

Laboratory Fee Schedule

Procedure: EZZ0084A


Trihalomethanes – Drinking Water
Synonym(s): THMs in Water
Requisition Form G-22
Test Description Trihalomethanes, EPA method 524.2
Pre-Approval Needed N/A
Supplemental Information Required N/A
Supplemental Form(s) N/A
Performed on Specimens from (sources) Environmental
Sample/Specimen Type for Testing Drinking Water
Minimum Volume/Size Required Two clear glass vials with Teflon (PTFE) lined screw-caps; 40 mL
Storage/Preservation Prior to Shipping

Iced (4°C)
Store samples in the dark

Transport Medium N/A
Specimen LabelingLabel each bottle with a water proof marker. Pre-printing labels is acceptable. Must match information on submission form. 
Shipping and Specimen Handling Requirements

Add 3 mg of sodium thiosulfate (or equivalent of a concentrated solution) to each empty clear glass vial (to dechlorinate).
Open the tap and allow the system to flush until the water temperature stabilizes, at least 5 minutes. Turn flow down to a smooth, pencil thin stream.
Remove cap from the bottle, tilt, and place under stream.
Fill the bottle with sample water gently, till the meniscus is level with the bottle top.
Carefully place the cap on the bottle, eliminating any air.
Mix gently by hand for 1 minute. DO NOT SHAKE.

Method EPA 524.2
Turn-around Time Samples must be extracted by the lab within 14 days of collection.
Interferences/Limitations Avoid collecting this type of sample in any situation where you can smell petroleum or solvent type fumes.
Common Causes for Rejection Insufficient quantity, unacceptable specimen type or source, improper shipping conditions, expired media or collection container, discrepancies between specimen label and submission form, incomplete or missing submission form
Additional Information

If the chlorine residual is >5 mg/L, additional buffer/dechlorinating agent is required.
For every 5 mg/L of chlorine above the initial 5 mg/L add an additional 3 mg of sodium thiosulfate dechlorinating agent. For example: a sample with 10 mg/L chlorine would require 6 mg of sodium thiosulfate.

Last updated June 29, 2022