Cross Much?

It is common practice in many areas to refrain from softening all water inside a home, specifically isolating fixtures like kitchen cold-water, bar- and vegetable-prep sinks, etc… There are a number of reasons to do this, but I’d like to address the wrong reasons first:

 

• Soft water has salt in it
• Soft water doesn’t have healthful calcium in it
• Soft water is corrosive
• Soft water causes heart attacks

 

The preceding fallacies are the most commonly cited reasons that I hear for plumbers and other water quality improvement contractors bypassing the kitchen cold-water sink from softened water. These fallacies have been debunked in WC&P  and in numerous other scholarly publications, but it will take many hours of training for the logic to penetrate for some. Many progressive plumbers and water system dealers are now plumbing all fixtures in the home with softened/conditioned/filtered water and then adding EDI or RO to specific points of use to help  clients who prefer the taste of purified water, or seek the additional health benefits from removing as much from the water as possible before adding aquaceuticals or drinking and cooking with the plain purified water. While  progressive dealers treat the water systematically, there are still countless other misinformed and/or stubborn installers who insist on plumbing hard water to the kitchen cold-water sink and sometimes, to other cold water fixtures. This common installation practice creates a potential problem for the entire installation…the dreaded crossover.

 

The problem

Crossovers are situations where two sources of water mix or blend in an unintended/unplanned  manner. The most typical crossover is when hard water at the kitchen sink crosses over through the faucet mixing valve/cartridge, then makes it way backwards to the water heater where it can contaminate the softened hot water with undesirable hardness minerals, chlorine, metals and possibly other contaminants. Crossovers can be difficult for service technicians to test for, especially if they don’t understand a truly systematic approach to troubleshooting.

Crossovers blending hard and soft water in the home can occur continuously or intermittently and when they do occur, they are irritating to the homeowner as well as repair technicians. An example of a typical continuous crossover condition is when no matter how hard the technician tries, the softener seems incapable of reducing  water hardness in the home by more than about 80 percent. An intermittent crossover is where the homeowner reports that the water sometimes ‘feels hard’ but is usually soft when the repair technician visits the home.

When suspecting a crossover, it is a good idea to gather and document the following data:

• Influent (untreated) hardness
• Effluent (treated) hardness
• Water pressure

An example of this situation would be:

• Influent hardness           20 gpg
• Effluent hardness           4 gpg
• Water pressure             75 psi

Assuming that the softener has already been tested and verified to be mechanically functional and the distributor pilot O-ring integrity has been confirmed, one can assume that a hard water crossover could be a problem here. The key to identifying and rectifying crossovers is to be methodical. Take the time to work systematically, and document your work as you go.

The most common method for physically diagnosing a crossover is to simply shut the soft water loop. This can be accomplished by using a three-way, ball-valve bypass or with specially ported two-handle bypass valves commonly found on professional-grade softeners and conditioners. Shutting off the soft water loop prevents water from flowing through the softener to the attached plumbing. It then becomes relatively easy to determine which fixtures are plumbed soft and whether a potential hard-water crossover exists. Once the softened loop has been shut down, the technician simply opens all the water-using fixtures in the building, from the lowest to the highest point, and waits an appropriate period of time for the fixtures to drain down (five minutes for every 1,000 feet [304.8 meters] of livable floor space is a commonly used figure). Once the fixtures have had an opportunity to drain, all softened fixtures should have absolutely no flow at all. If the kitchen cold (or any other faucet/fixture) is running at full speed at this point, then it is clearly evident that it is ‘plumbed hard’.

By simply closing the hard feed water stop to the fixture, one can determine if the crossover is occurring there. Let’s say that the kitchen cold water is running full flow and  the technician turns off the angle-stop under the counter…by turning off the angle-stop, the hard-water feed is unable to pass through the faucet. The technician can now turn the soft-water loop back on and test water quality, after rinsing for an appropriate period of time. If the water is suddenly soft, this is proof positive that a crossover condition has been occurring in the home.

Fixing crossover is relatively easy, by taking a pro-active approach during installation of the water treatment system.  Installing a simple check valve on the hot water side of the afflicted fixture will permanently prevent hard water from moving backwards to the water heater or from contaminating other fixtures.

Compounding the problem

In certain extreme cases,  hard-water crossover doesn’t just inconvenience  the homeowner by pushing hard water backwards to the water heater and the installer trying to resolve the issue. Sometimes the problem can be much worse.  During regeneration, the water softener becomes the path of least resistance for hard water crossing back through the water heater. This can introduce piping hot water back to the softener during backwash and potentially damage the polyethylene distributor and riser assembly, resulting in catastrophic resin release into the building. The solution is to install a spring check valve on the outlet of the water softener.

Best Practices

This discussion about crossovers reminds one that it is always a good idea to use industry best practices when installing water treatment equipment. Yes, it will cost more to do things right, but it certainly results in fewer call backs and happier customers.

Current industry best practices include installation of the following:

 

• Inlet water pressure regulator
• Inlet pressure gauge
• Inlet sample port
• Bypass that allows for proper soft-loop isolation
• Outlet sample port
• Outlet pressure gauge
• Outlet check valve

Do the very best job that you can, and your customers will appreciate it.