Question:

I have a 1” Conbraco model number 40-500 that I think has been damaged from freezing over the winter. Can you give me some information on repairing this unit?

Doug:

The Conbraco model 40-500 is a pressure vacuum breaker that started production in 1991 and was discontinued in 2003. The body of this assembly is made of bronze material. The internal check poppet and float are made of plastic, while the spring, retaining screws and retainer are made of stainless steel. No special tools are required to service this unit.

Mark:

The first step is to remove the canopy. The canopy is the metal, bell shaped protective cover on top of the unit. It is secured to the bonnet with two phillips screws. Once the canopy has been removed, the top of the bonnet is exposed. The bonnet assembly is threaded into the bronze body and is sealed with an o-ring. The bonnet will unscrew counter clockwise and there is no spring load. Be sure to place the wrench on the top bracket of the bonnet to avoid damage.

Doug:

Once the bonnet assembly has been removed, the float assembly is free. The float simply moves up and down within the body and is guided by a stem on the bonnet. If the stem or spring has been damaged, the bonnet assembly must be replaced. The rubber float disc can be removed by simply pulling it from around the groove in the float.

Mark:

The next component you will need to inspect is the check assembly. The check assembly is located in the lower body and is spring loaded. The check poppet and check spring are held into place by a retainer. The retainer is a flat metal bracket that locks into the bronze body. To remove the retainer, simply push down and rotate until it clears the tabs on the body. Once it is removed, the spring and the check poppet are free.

To replace the rubber check disc, remove the retaining screw and guide from the check poppet. Be aware that the check seat is part of the body. If the seat is damaged, the assembly must be replaced.

Authors
Mark Inman	In our line of work, we field questions from contractors and technicians concerning repairs, installations and general backflow prevention practices. We’d like to share some questions that we receive, as well as our answers. Everyone has different opinions on these subjects and we would like to hear yours. Contact us with questions and ideas via email at: imark@backflowparts.com or mail us at: American Backflow Products Co., PO Box 37025, Tallahassee, Florida 32315.
Doug Taylor