People are concerned about their water quality.

By Ron Perrin            (c) 2010 all rights reserved

Cleaning water storage tanks is a positive action to address this problem.  While a few states require water storage tanks to be inspected only Florida requires tanks to be cleaned at this time.  The few states that do require tanks to be cleaned are content with the outdated AWWA methods of draining the facility, putting an inspector inside to check for structural soundness, and paint conditions, few inspectors pay a lot of attention to the sediment on the floor.  The tank or tower is then decontaminated by super chlorinating the water as it is filled.  That water is dumped, and replaced with fresh water that is tested before the tanks returns to service.  This method that has been in place for over 25 years and is a good way to disinfect any contamination an inspector may have introduced into the tank.  It will also kill a majority if not all of the bacteria and viruses that may be on the interior walls or on the surface of the sediment in the floor of the facility.

This method is NOT CLEANING the tank.  You can inspect & disinfect the water storage tank or tower and NEVER CLEAN IT.

If there are colonies of bacteria in and under the sediment before this process many will survive the disinfection process using the sediment for cover.  Protozoa like crypto can even survive the decontamination process on the surface of the sediment.  It has been proven that the only effective way to rid a water storage facility of crypto is physical removal.   What this decontamination procedure will do is return the tank to a condition that will pass a water quality check, while problems continue to grow in the sediment.

Most water storage tanks & towers are not designed to be cleaned.   The water drained goes directly into the water system.  There is not a “DRAIN PIPE” or “Wash Out Port” on most water storage tanks or towers.

The engineers that designed most of the  the tanks & towers in service today never thought about needing to clean them.  The thinking was this- It is storing perfectly clean and treated water in a closed system from the water plant, the water will be in the tank until it goes to the tap and is used by the consumer.  How could it get dirty?

Since 1990 tanks have been routinely inspected by divers, ROV’s and remote underwater video cameras.  What we know for sure it that over time WATER STORAGE TANKS accumulate sediment.

When tanks are drained & inspected what appears to be 1/4 or 1/2″ of insignificant sediment on the floor of the tanks, may actually be two or three inches of semi-liquid habitat on the floor of the tank that can support & hide billions upon billions of contaminates.  Seen with underwater cameras while the tanks remain in service we are only now beginning to understand how much of a threat sediment on the floor of a potable water storage tank is to public health.   Many states without any inspection rules are allowing feet of sediment to accumulate.

Tank Cleaning Methods:

Some attempt to pressure wash the facilities.  Workers are sent up and into a water storage tower with pressure washers and told to clean the tank.  They see a big floor drain in the center and of course push everything into it.  There is no where else for it to go.  Every thing that is cleaned with a pressure washer is then pumped right back up into the tanks when the facility goes back into service.

From the drawing board tanks & towers need to be designed with clean out drains & clean out valves.  Regulators need to understand that the AWWA rules for inspecting and disinfecting water storage tanks are antiquated.  The State of Florida is the first to understand that regulations must be in place to CLEAN tanks at least once every five years, in addition tanks that are attached to a raw water source must be cleaned annually.

For More information on tank & tower cleaning visit http://www.ronperrin.com

Polluted Drinking Water

Water Storage Tower Being Cleaned

People are concerned about their drinking water, and they should be.

To properly clean most water storage tanks the sediment must be PUMPED out.  Removing the sediment to the yard of the facility is the only practical way that the tank is really cleaned.  A Potable Water Dive Crew using equipment that is purchased for and only used in potable water is a economical way to keep the facility clean.  Wearing dry suits that completely seal the diver in his own environment the diver can be washed down with a 200ppm chlorine solution.  This removes the need to “decontaminate” the entire tank after the inspection or cleaning.  The diver can then enter the facility and vacuum  ALL LOOSE sediment from the floor of the tank, completely removing any contaminate that may be using the sediment for cover.

This method leaves the tank much cleaner than pressure washing or the traditional bucket & shovel.  It also saves water, using only a fraction of the water lost draining then disinfecting the tank.  Saving the utility time and water results in a saving of utility funds while providing customers with cleaner drinking water.  When human health is a risk, the savings cannot even be calculated when you consider that some basic housekeeping may keep your utility from being next weeks headlines regarding contaminated drinking water.