If you have a defective zone valve, the problem could be in the unit, or isolated just in the head. As a less expensive alternative to replacing the entire zone valve (if your problem is in the head, of course), you can purchase a Zone Valve Replacement Head, a twist on part which is easy to install and maintain.
Zone Valves and other Taco Heating Products can be found at www.supplyhouse.com
Zone Valves and other Taco Heating Products can be found at www.supplyhouse.com