The extensive use of high-pressure cleaning equipment in tunnel washing is bringing more maintenance problems from the high relative humidity and water mist this equipment generates.

Continual exposure to this high-moisture environment can cause extensive damage to buildings, equipment and associated sub-systems in the commercial carwash.

These expensive problems occur in both new and retrofitted facilities. And although they cannot be completely eliminated, the damage can be minimized with changes in building design and operational techniques.

The first control scheme is to cut creation of the mist at its source.

In high-pressure cleaning systems, the pressurized water is used to replace the mechanical friction of brushes or cloth. Water, weighing 8.33 pounds per gallon, impacts the vehicle with a cleaning force generated as a product of the mass (expressed in gallons per minute or GPM) and the velocity (expressed in pounds per square inch or PSI).

To a point, increasing the GPM or PSI will increase the cleaning power of the system, but the amount of mist generated is directly proportional to the PSI.

Unlike increased GPM, higher pressure does not necessarily increase cleaning power. As the system pressure is increased, the water stream from the spray nozzle will break up and start to atomize into smaller droplets.

These droplets rapidly decelerate and lose their impact power on the vehicle surface. With any pump/nozzle system, there is a peak pressure, which if exceeded, will actually decrease cleaning effectiveness.

Above this design pressure, more mist and less cleaning will result.

Solution: Set system pressure to the manufacturer's design pressure.

The spray nozzle is subject to wear from the high-pressure water flow. If the system uses reclaimed water with high suspended solids, the wear increases. Worn, clogged or ineffective nozzles produce spray patterns that increase the atomization of the water, which increases mist.

Blasting water into the "open space" between vehicles is a waste of energy and increases equipment wear.

Source point control can do only so much to prevent the generation of water mist. Once the mist is present, the "building systems" (structural, architectural, electrical and HVAC, for instance) must be protected from damage by water infiltration, corrosion and associated damage.

The first line of defense is to remove as much of the water vapor in the air as possible.

Water may condense or settle on the flanges of bar joists and other building components and travel under the roof to damage ceiling tiles, air-handling equipment, walls and even cash registers and computers as it drops into other areas of the building.

In freezing temperatures, the humid, misty air from the wash bay infiltrates the areas over the inhibited parts of the carwash. The water freezes on the underside of the roof then thaws and rains down on the office and lobby areas, causing unsightly and expensive damage.

· Contain the water mist to the bay or tunnel area by sealing possible paths where water could infiltrate.

· Seal openings around bar joists and building support beams to contain the water/mist in the bay. An effective way to prevent water traveling along the flanges of I-beams and bar joists is to block the path with beads of RTV sealant that force the water to drop off the flange.

· Establish a vapor barrier between the equipment bay and the lobby/office area (and equipment spaces) that extends from the floor to the underside of the building's roof. Plastic sheeting overlaid with fiberglass board or vinyl siding works well.

· Make sure "attic spaces" are properly ventilated.

Equipment and electrical rooms may have standing water on the floors and expensive capital equipment covered with rust and corrosion due to the high relative humidity present in these areas.

Not only is moisture damage expensive, the danger to carwash and service personnel from slippery footing and water/electricity mix cannot be understated.

· Make sure the equipment and electrical room doors are kept closed; install automatic "door closers" to limit this access path.

· Provide and ensure that floor drains are clean and free-flowing.

· Install and maintain ventilation equipment to remove moisture from these areas. Use "heat exchangers" as necessary

· During construction or equipment installation, use PVC and other non-corrosive plumbing and electrical piping and fittings. Most codes now allow the use of PVC conduit and water/air piping, which can lower both installation and total life cost.

· Consider "point-of-use" ground fault interrupters (GFI) electrical receptacles for use in all tunnel and bay areas. Although GFIs are prone to "false trips" in high-moisture areas, they can be quickly reset, and the increased safety margin is worth the effort.

Hugh Oldham is a carwash service manager and regular contributor to Professional Carwashing & Detailing.