What to do when backflow occurs
Flush, flush, flush! For safety.
Flush, flush, flush! For safety. Not your toilets’ but your customers’ water systems after any backflow incident or breach in the line.
With all the federal and state water-protection programs we have in place to ensure we are supplied with high-quality drinking water from the water purveyor, there still is a possibility of getting contaminated water from your tap.
The water purveyor requires backflow-prevention devices at many areas to protect that water from any cross connections that could potentially contaminate this water. When the piping is installed or replaced in the distribution lines, they are treated with chlorine at a specific amount for a specific “contact time” that ensures the piping is not contaminated. On top of that, our plumbing codes give us more confidence that the high-quality water being supplied is protected and distributed to every customer by regulating the pipe, fittings and fixtures used within this system.
Awesome! What could go wrong?
With all our safeguards in place, backflow conditions can and will occur. The better we educate our customers regarding the dangers, the safer our communities will be. But no matter how diligent we are, we can be affected by other people tied into the system.
After you, as a responsible contractor, install vacuum breakers on each hose bib, PVB (pressure vacuum breaker) for irrigation, RPZ (relief pressure zone) for the domestic water and DC (double check) for the fire system, air gap for the dishwasher, etc., to protect the water system, and 90% of the customers on the system do the same, you still have the house (or houses — which usually is the case) down the block installing a booster pump system without the proper check valves, filling up their pool from an unprotected hose bib or performing any noncompliant plumbing repairs that have or will result in possible cross connections.
Backflows can be caused by backpressure and back siphonage. A simple example of a back siphonage condition would be if a vehicle ran over a fire hydrant. This high volume of water rushing through this broken hydrant can siphon water from the system (for example the hose filling the pool). This pool could be highly contaminated and this back siphonage would be pulled into the water-distribution system. Back pressure can be caused by a booster pump system that was installed to increase the house pressure above the incoming supply pressure or even thermal expansion from a boiler or water heater.
If your customer calls to have their water main repaired, it usually is not a difficult task depending on the location. After the water is shut off and the mud and water is removed to expose the failed piping, the repair is completed. The water system is recharged, flushed and back to static pressure for a quick test. Backfill and clean up, the customer is happy.
Within this repair is our issue. What is our procedure to protect us from contamination? Is the flush enough? How much water should we flush? How much water does it take to flush out the fertilizer and chemicals that entered the failed piping? If it was a PVC repair, what is the required amount of water needed to flush out these chemicals?
The previous scenario has some obvious issues with contamination that will occur on every repair but what about other repairs? Plumbers always are getting into the customer's water system for repairs, remodels or even fixture change outs. Each time we breach the system there is a chance for contamination.
Contamination from repairs or installs
Some companies are sewer and drain only but they do have plumbing skills. If they show up to a mainline stoppage and the cleanout is in the garage wall behind the water softener, and if they remove the softener to clear the stoppage, the contamination into the water system is greatly increased.
After opening the cleanout, sewage begins to overflow before the stoppage can be cleared and the overflow contaminates the flex lines that were left on the ground. The garage is then cleaned up and the softener is put back together. The customer’s flex lines to the softener are reinstalled without being disinfected. This can happen to the most experienced contractor whether it’s complacency, a very busy schedule or the homeowner that may do this on their own with a rented piece of equipment.
What if your customer used a toilet on the east side of the house while the water system was shut down and the only portion of the system that was flushed out after the repair was the cold water on the west side at the bathtub (this is the easiest place to flush so you do not get any debris in the aerators or in the water heater)?
The east-side toilet will then fill the tank when the water supply is turned on. When this happens the contamination could have compromised the piping on this branch. If your kitchen is also fed off this branch and your customer grabs a large glass of tap water, they could be drinking contaminated water.
So, with all the regulations, codes and backflow protections out there, we still have this possibility of a potentially devastating incident that could occur. We currently rely on a good flush after repair and hope the residual chloramines will be sufficient protection from this contamination. If the contamination is more severe, a call to the water purveyor would be recommended.
When in doubt, boil water for drinking. When doing this, remember besides letting it cool before drinking, boiling water will remove the good and the bad so this water has a short shelf life for drinking purposes as the chloramines that keep it protected have been boiled out.
As the old saying goes, “The plumber protects the health of the nation.” Plumbers have prevented more disease than doctors have ever cured.
This article was originally titled “If it can backflow, it will” in the September 2018 print edition of RJ 2.0.