The first flush of bacteria-free water is a problem that plumbers have been trying to address since the days when indoor plumbing was in its infancy. What’s different now, however, are the computerized sensors and microprocessors used to detect stagnation or contamination in plumbing systems. You can learn more in this post regarding this process.
Procedure For Flushing Domestic Water Systems
Follow the steps given below to record the flushing activities. All buildings that have been closed for a lengthy period of time should have these flushing procedures performed by building owners or maintenance employees. This will lower the danger of disease and death as a result of a building that has been vacant for a long time.
The goal is to replace all stagnant water in the potable water system with fresh water from the municipal distribution system that contains a disinfectant residual.
During flushing activities, individuals should wear an “N-95 respirator mask” and Personal Protective Equipment. Complete the following flushing method in the following order when executing a flushing operation:
1. Take a sample of first-draw water to assess the residuals of water treatment chemicals in the building service pipe. Collect the sample at or near the meter and backflow preventer, or where the service pipe enters the building, from a monitoring point in the service pipe. Take note of the chemical kind of water treatment used by Water Utilities. This pre-flush test should be used as a benchmark for comparing pre-flush and post-flush water quality.
2. Collect a water sample from at least five (5) different distant sites inside the building to evaluate the building’s water chemical residuals. These areas should be noted to serve as a pre-flush and post-flush baseline for comparing pre-flush and post-flush water quality.
3. Determine the size and length of the building service pipe.
4. Multiply the volume in the building service pipe by 2 for the needed volume to be flushed from the service piping, depending on its size and length (Linear feet of service pipe x volume per foot from #3 above) Service pipe volume: Note 2 – Volume of water must be flushed via the service pipe at a velocity of 3 feet per second.
5. Determine the number and position of fixtures that must be flowing at the same time in order for the service pipe to have a 3 feet per second velocity. Hose valves will be flowing from the requisite number of flushing sites to provide a flushing velocity high enough to scour bio-film and silt from the service pipe at a flow rate greater than 3 feet per second.
6. Perform and record a pre-flush water quality test at the water service entry and at 5 distant fixtures to assess water quality and treatment residual. There should be a minimum of 1 part per million (ppm) of free chlorine at the building service entrance and 0.5ppm at the furthest fixture.
Consult a professional for suggested minimum water treatment chemical levels or as specified by the facilities’ water management program team) entering the building for buildings with additional water treatment chemicals in the utility water. If the water quality is excellent, there is no need to cleanse the service pipes.
7. If the pre-flush water quality test indicates any water discoloration, odor or lack of sufficient free chlorine residual, perform and document a full velocity flush of 3 feet per second for the building water service pipe as follows:
a) Determining the proper number of fixtures to flow to flush the building service pipe at a minimum velocity of 3 feet per second, based on the size of the building service pipe size.
b) The flow can be through a combination of fixtures that can be flowed through a combination of hose bibbs, hydrants, and fixtures near the water service entrance. and test the potable water service connection until a disinfectant residual is detected or a volume equivalent to double the water held in the service connection is cleared, whichever occurs first.
8. After 30 minutes of flushing the building service pipe, if no disinfection residual is identified, stop flushing and do not continue with the potable water system flushing operation. To get chlorinated water close to the building, contact the water company and request that they or the fire department flush the water mains via neighboring fire hydrants.
If the building is part of a cluster of buildings or in an area with a lot of vacant structures, flushing a hydrant at the end of the water line could be a good idea.
9. If a disinfectant residual is detected on the building service pipe, open some faucets farthest from the building water service and at the end of each major branch main of the water distribution piping, and let the hot and cold water run continuously until a disinfectant concentration is detected close to or equal to the chlorine residuals in the building service connection.
A branch main is a major distribution pipe (usually larger than 34 inches in diameter) that feeds other branch pipes and fixture branch pipes.
10. Connected to the potable water system, flush any remaining fixtures, tanks, and appliances (including exterior outlets). Flow water from the hot and cold water systems at the same time. Depending on the kind of fixture, the following flushing technique should be used:
- For 1.6 GPF fixtures, toilets and urinals must be flushed 5 times each.
- All other fixtures, including hot and cold water, with flows of 2 GPM, must be flushed for a minimum of 3 minutes each.
- Flushing any water storage or hot water tanks at a pace of at least 2 times the capacity of the tank is recommended.
- Water pressure should be removed from hydro-pneumatic and thermal expansion tanks such that all water inside the tank is discharged completely.
Infra-red faucets shall be operated for a consecutive period of time equal to 20 cycles for every 10 feet of 3⁄4 inch branch piping.
11. The person performing the flushing operation should record the room number, the fixture type & ID, flow rate in GPM, start time and temperature, end time & temperature, chlorine residual near the end of the flushing operation, and notes or observations for each fixture like the ambient temperature of the room, when the water temperature starts to change indicating fresh water is arriving at the fixture, chlorine residuals in the first draw and at completion.
Thereafter until a minimum chlorine residual of 0.5 ppm is achieved at each fixture. Take a water sample in the first draw and upon completion of the flushing and Note any water discoloration, odor, etc) for the first draw and test the chlorine residual in the final draw at the completion of the flushing operation.
If the measured chemical residual is insufficient to control bacteria growth, perform and record the flushing operation as shown on the following “Fixture Flushing Record Sheet.”
12. The safe drinking water legislation requires the water company to supply safe drinking water to the building service meter. Note that utilities may fall below the safe drinking water act’s quality threshold for three consecutive 6-month reporting periods before having to alert the public. The building owner is responsible for ensuring the water safety of the structure.
Water quality on the building side of the water meter is not the responsibility of the drinking water supplier. A water utility should endeavor to offer high-quality water, but we all know that water utilities can’t always guarantee safe drinking water due to water main breaks, construction, fires, and other interruptions in water main flows that result in murky water and high bacteria levels.
As a result, the building owner has a duty and obligation to monitor the water quality entering their structure and to implement a water management plan to handle water quality concerns.
Water flows have been decreased to less than 20% of what they were previous to 1992 in this era of water conservation. The flow in the mains has been decreased to the degree where water treatment chemical residuals have dissipated to the point where bacteria growth in the mains can no longer be controlled. Building owners must monitor the incoming water and, if necessary, use extra water treatment devices to alter the water quality.
When selecting a supplemental treatment system, a building owner should check with a specialist to see whether they need any license, certification, or filters.
13. Flushing should be undertaken promptly prior to re-occupancy when a building is empty for more than 7 days or for a length of time agreed upon by the building’s water management program team. When a building is empty for more than four weeks (28 days), or for a period agreed upon by the building’s water management Program team, flushing and disinfection should be performed promptly prior to reoccupation.
Note: Flush all sinks first, then flush showers, then flush water closets & urinals. Fixtures with flush valves can become clogged with debris and not flush properly if they are flushed first. If flush valves do not perform properly and run on, shut off water and remove the diaphragm and clean the orifice. When done flushing, remove faucet strainers and showerheads and clean or replace them.
Storage Water heaters should be maintained at a minimum temperature of 140F or higher in the tank as needed to offset heat loss and maintain a minimum hot water temperature at the lowest temperature in the system a couple of degrees above the Legionella Growth temperature of 122 F. (124 F) on the hot water return pipe connection to the water heater.
The hot water return pipe just before the cold water connection to the water heater is the lowest temperature point in the hot water system.
To prevent Sclading, all shower valve maximum temperature limit-stops should be adjusted to a maximum temperature of 115 F at showers & bathtubs to prevent scalding. (Consider a maximum temperature limit stop setting for showers and tub/showers of 110 F at hospitals, nursing homes, and similar facilities where there is the additional risk of scalding.)
Hot water temperatures may rise in storage and distribution pipework and should be decreased or regulated at or near the fixtures by using code-compliant temperature limit-stops on tub/shower valves or temperature limiting valves that are appropriately configured to limit temperatures at the point of usage.
Following these rules, every fixture in the facility should be cleansed until the water treatment chemical residuals are at an acceptable level. Following these precautions should prevent tens of thousands of employees from contracting Legionnaires’ disease and other waterborne diseases linked to stagnant water.
A vital part of your home plumbing system is the water heater. But which type should you buy? For more information, see Gas Vs. Electric Water Heaters: The Straight Facts.
Frequently Asked Questions
How do you flush bacteria out of water pipes?
A: You need to use a solution of bleach and water that is mixed in the ratio of 2 parts bleach, 1 part water.
How do you get rid of Legionella in pipes?
A: Legionella is a type of bacteria, usually found in groundwater. This can get into your pipe system and grow into colonies that will multiply exponentially if they are not dealt with properly. One potential solution would be to use chlorine gas as this kills off the bacteria quickly and effectively.