By Gary Battenberg
In the July 2010 issue of WC&P, the comparative operating costs of conventional water treatment versus whole-house reverse osmosis for the purpose of finding the best treatment process for the challenging water in northern New Mexico were discussed. That article (see Comparative Operating Costs of Conventional Water Treatment versus Whole-House Reverse Osmosis) concluded that advanced membrane technology was the most efficient method for converting 80 percent of the available daily volume to high-quality water for domestic use.
Part One of this article details the site visit to collect water samples for testing and to confirm hydraulic characteristics of the well water supply. Evaluation of the original equipment installation, assessment of environmental conditions and electrical supply are also noted for subsequent system design considerations. The following field report is based on actual email correspondence between the contractor and the client’s attorney. It recaps the assessment of current equipment condition and translates those field findings in layman terms for a prospective customer in a way that is understandable, while building sufficient value to close the sale.
Names have been withheld for privacy. Because the owner resides in another region; communication was accomplished via email and handled by the client’s attorney, adding a dimension that made this process interesting to say the least.
Well pit inspection
Found to be in apparently good condition, it showed no signs of excavation degradation or rodent intrusion. It featured a hi-flow sediment filter, plumbed into the main water line, downstream of the pressure tank. This was deemed a risk for eventually causing a low-flow and low-pressure condition to the service plumbing in the house and was considered for upgrade and relocation to the equipment service gallery of the mechanical room. In preparing the sample point for the water test draw, there was a very distinct sulfur (rotten egg) odor typical of hydrogen sulfide. It was tested t using a portable test kit, which confirmed the presence of 1.25 mg/L, and noted it for future reference in the total system design.
Hydrogen sulfide (H2S) is a corrosive and flammable gas often found dissolved in well water and typically accompanied by iron and low pH values. Hydrogen sulfide develops from decaying organic matter, from sulfate reducing bacteria (SRB), and from petroleum refining. H2S formation can be catalyzed by the magnesium anode rod in the water heater. Anaerobic sulfate reducing bacteria can live and proliferate in a water heater when the temperature is below 140 degrees Fahrenheit. To produce H2S, SRB need only a ready source of sulfate ions in the incoming water supply and a static supply of electrons as provided by the water heaters’ anode rod.
Of the several methods for removing hydrogen sulfide from a water supply, and the required final water quality specification of the owner dictated the type of treatment recommended to balance the entire treatment array. Additionally, the results of the laboratory analysis were interpreted to determine the most cost effective and reliable system for the quantity needed to manage the household. An equipment proposal and technical synopsis was provided after review of the laboratory analysis.
Photographs
From left to right: 1) Dried deposits on filter housings, unsecured high-pressure tubing arrangement and electrical outlet at floor level is subject to water spray. 2) Confusing plumbing array, with dead legs and uncapped piping termination. 3) Pump connection utilizing reducer bushings and flexible PVC tubing.
A series of photos of the existing equipment layout, piping and instrumentation were taken to provide a ready reference detail to facilitate the report. Entry door sizes and available floor space were recorded so that all recommended system component dimensions could be checked against the minimum entry opening, to ensure easy removal of expired equipment and placement of new, high efficiency equipment.
Plumbing evaluation
Corrosion of the copper piping, where it transitioned from incoming PVC pipe from the well, was due to a combination of faulty pipe joining technique, disrupted grounding and the corrosive tendency of H2S. All piping, up to and through the pretreatment phase of the system, were remade with corrosion-resistant piping materials and transitioned back to the copper service plumbing, and a contiguous ground was re-established. The final product water introduced to the service plumbing would be of very high quality with a pH stability that would not attack the metallic plumbing components nor corrode the anode rod of the water heater. The copper piping appeared to be affected by galvanic corrosion as evidenced by the green and white buildup on the piping surface and at the mechanical joints. Galvanic corrosion was caused by joining of dissimilar metals (such as galvanized to copper) without benefit of a dielectric union or a non-ferrous metal (such as bronze). Additionally, with the plastic to copper transition, electrolysis set in because the contiguous ground from the electrical panel had been disrupted, creating an open neutral ground and thereby initiating the galvanic action observed during evaluation. No ground wire jumpers spanning the dissimilar piping materials to maintain the contiguous electrical grounding were found. Cold water service flow inside the house appeared to be of sufficient volume at each tap. Hot water flow was significantly less and may have been caused by excess calcium carbonate build-up in the bottom of the water heater, impeding the flow of hot water to the service plumbing. Calcium carbonate crystals were observed in the aerators of several faucets in the home; cleaning the screens failed to improve the flow. There was also a problem with the diverter cartridges inside the body of the faucets that require a service plumber to restore the faucets to optimum service flow. Hot water was flowing from the heater, as evidenced by the elevated temperature of the exposed hot water piping in the mechanical room.
System component evaluation
With regard to the existing system array, it was quite evident that several contractors had attempted to improve and/or modify the existing system over the years. Shabby workmanship was very evident by the fact that the heat exchanger had been overridden and left in place instead of being removed. The raw water bypass arrangement was convoluted and difficult to understand. The service and bypass valves should have been marked ’Normally Open’ or ‘Normally Closed’ to prevent cross contamination between raw and treated water. Access to this by-pass arrangement was buried behind the automatic water filter and not easy to use or understand. The filter was non- functional because the timer motor was burnt out, as was the drive motor. Therefore, the parallel hi-flow safety filters were taking the entire filtering load for sulfur conversion. Plumbing of parallel hi-flow filters was not balanced in a ‘first-in-last-out’ configuration, which caused unequal flow through the filters and poor performance. Additionally, improper plumbing technique and material selection were quite evident throughout the plumbing system; leak repairs had been made where a union connection would have made repairs quick and easy without exposing the plumbing system to atmospheric conditions that typically contribute to bacterial growth in the water system. There were several locations in the plumbing arrangement where components had been removed; piping connections were open to the atmosphere or capped off, creating a dead leg in the plumbing. That condition made it very hard to maintain bacteriologically safe water for consumption. Should a valve have been opened or a pipe broken on one of these dead legs, severe water damage could have resulted.
RO system
The existing RO system was antiquated and it was clear that the system was field engineered and pieced together by marginally trained installers. The rotary vane pump and motor assembly were sitting on the floor instead of being mounted on a stationary structure, on the RO wall bracket or mounted on an inertia base with vibration dampers. Flexible high-pressure tubing was improperly routed from the pump to the membrane housing and could easily have been damaged. Those flexible tubes should have been anchored to the wall bracket to reduce both the installation profile and potential for damage to related components. Additionally, had a water leak occurred, that pump and motor assembly would have been subjected to water spray, which could have resulted in severe electrical damage that would have destroyed that critical component. Electrical outlets were exposed to potential water spillage during filter replacement because they were close to floor level instead of being installed above potential water exposure levels. Those low mounted outlets were not GFCI equipped to prevent electrical shock hazard in that environment and should have been relocated and properly updated for that equipment gallery.
The RO system was checked for automatic float initiated operation and found to be working satisfactorily. The pre-filter housing on the RO showed signs of leaking (between the filter bowl and cap), indicating long over due O-ring replacement. Previous service technician(s) had used extreme force to seal the housing, causing the O-ring to collapse. The pinch area in the filter bowl had been exceeded, as evidenced by the lack of a small gap between the filter bowl and the cap. Over tightening of the housing could have caused failure of the filter bowl and a serious flooding scenario would have resulted. The O-ring should be replaced at every filter change to ensure long-term component integrity.
Storage tank
The 300-gallon (1135.62-liter) RO water storage tank generally appeared to be in good condition and suitable for continued use; however, there was no breather kit to prevent atmospheric contamination of the water. A breather kit would filter the air being drawn into the storage tank when water was being transferred for internal use, to prevent collapse of the storage tank. It breather kit would have permitted the tank to be sealed around the man way (what is man way?) in the top and prevented atmospheric intrusion of airborne contaminants entering the purified water. The manway is the access port in the top of the tank for access to level switches and water connections. This tank was checked and found to be constructed of HDLPE (high-density linear polyethylene), which complies with FDA Regulation 177.1520 and NSF Standard 61.
Transfer pump
The transfer pump was free standing on the floor and held stationary only by the interconnecting piping to the pressure tank. Again, the pump should have been mounted in a stationary configuration to prevent potential damage to the pump, piping, pressure tank or post filter connections. With the exception of the tank shutoff, there were no service valves in the transfer pump circuit to isolate the pressure tank or the post filter to facilitate service of these components. Water spillage during filter replacement would have doused the pump and adjacent wall outlet, resulting in potential electrical shock hazard. Suction tubing from the tank valve was flexible reinforced PVC; it provided no stability for the pump. The tubing was 3/4-inch (19.05 mm) diameter and smaller than the inlet connection of the pump. Properly done, the suction pipe should always beat least one size larger than the discharge piping, in this case 1.25-inch (31.75-mm) suction x 1.0-inch (25.4-mm) discharge. That configuration was important to maintain adequate flooded [volume] suction to the pump inlet to prevent cavitation within the pump cavity. (Cavitation is that condition created where the pump discharge volume is greater than inlet volume, which allows the formation and collapse of a gas pocket or bubble on the blade of the pump impeller. Collapse of this gas pocket or bubble drives water into the impeller with terrific force that can cause pitting on the impeller.) Brass reducing couplings were used to fit the pump suction and discharge ports, instead of corrosion proof thermoplastic pipefittings used elsewhere. That was not a proper pipe joining method and clearly displayed a lack of training for the installer.
Missing link
Conspicuously absent from the treatment system was UV disinfection. Water that has been purified, stored in an atmospheric tank and re-pressurized for domestic use must be disinfected to prevent bacterial growth and migration to the service plumbing. Water should be passed through a UV system, with a bleed line back to the storage tank, to maintain living (moving) water and prevent the UV system from overheating, which will keep water in the tank disinfected and provide peace of mind for the homeowner.
Technical observation
Based on its observations, the contractor recommended a complete system replacement (with the exception of the storage tank). All other existing equipment and related piping was cleared out and replaced with a new, high recovery water system that represented a considerable component upgrade from a system that was field engineered, providing substantial savings in installation costs as well as consistent operational benefits. The entire system, including the specific location of piping connections and components, was carefully designed for easy service and maximum efficiency.
Part Two will present the proposal (including interpretation of the water analysis, equipment list and array and technical synopsis of the system function and maintenance requirements. Stay tuned.
About the author
Gary Battenberg is Managing Director of Santa Fe, NM-based Good Water Company, Inc. He has 29 years experience in the field of water treatment processes, including equipment design and manufacturing utilizing filtration, ion exchange, UV disinfection, RO and ozone technologies. Battenberg is also a member of the WC&P Technical Review Committee. Contact him via electronic mail at [email protected] or call him at (505) 471-9036.
About the company
Good Water Company serves Santa Fe and Northern New Mexico residential, commercial, farm and ranch customers with remediation for severe groundwater problems, specifically arsenic, fluoride, nitrate, uranium, silica and high TDS. The locally owned water treatment business, founded in 1988 and purchased by geologist Stephen Wiman, Ph.D. in 2004, is committed to pursuing the most efficient use of precious water resources. Its goal is to minimize the use of chemicals and reduce wastewater in the treatment process. Dr. Wiman applies scientific principles and fundamental water chemistry for each individual application and offers state-of-the-art equipment from a variety of manufacturers to solve complex water problems.
About the product
The test kit used in the evaluation was the HACH Model HS-WR, Catalogue No. 2238-0.