Crossover Problems

Crossover is a problem that occurs when hot water is prematurely mixed with cold water or cold water is prematurely mixed with hot water. In both cases however, the mixing is taking place somewhere in the plumbing system other than where it is intended to be mixed.

Common causes of Crossover Problems:

Low Flow Shower Heads:

In the case of low flow shower heads, users open up the hot and cold valves for the water to be mixed, however because the low flow head restricts output, the excess water that is not consumed, moves down the loop for the next dwelling unit to use.

‘Shut Off’ Shower Heads:

One water conservation tool is the shut off shower head. The intended use of this product is for a user to get wet, then shut off the water while the user lathers up, then the user turns the shower head back on and rinses off. The problem occurs during the shut off period. During the time at which the shower head is in off mode, 100% of the mixed water that is not being used by the intended recipient is sent down the loop to others at a significantly reduced temperature. In some cases this is taken to extreme in which users use the shower head as the on/off switch, in which case the entire hot water loop is compromised. Depending on the configuration and demand of the water system, these type of devices also cause significant hot and cold water surges.

Sink Based Dishwashers:

In some communities dishwashing occurs by portable dishwashers that connect to the sink outlet. Crossover occurs in this scenario much like the shut off shower head, in that while the sink valve is open, crossover will occur.

Worn Out Single Handle Valves:

In all modern plumbing environments the hot water mixing within the sinks and showers occurs at a single handle valves which mix the water just prior to consumption. Manufactures of this type of valve include Delta, Mix-it, Moen to name a few. Over time these valves wear out and crossover occurs. Depending on the manufacturer the crossover problem will affect your system differently:

Moen

The Moen type of valve utilizes a cartridge where mixing takes place within the cartridge. Replacing the worn out cartridge will usually fix the problem and a new cartridge will last from 1 to 5 years. We recommend using a Moen replacement cartridge # 1225 magnum if the valve is compatible. Nomix also makes a cartridge with a lifetime guarantee.

Mixet

The Mix-it type of valve utilizes the valve cartridge as well as the valve cartridge for sealing when mixing hot and cold water. Replacing the cartridge in a worn valve will not resolve the issue and you will still have a crossover problem. There are two alternatives;

1. Replace the entire valve or
2. Install an aftermarket Nomix cartridge. The Nomix cartridge has a lifetime guarantee.

Other Manufacturers

We recommend contacting the manufacturer’s representative.