water hammer from hell

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    • #274318
      MasterPlumbers
      Keymaster

      I am a remodeling contractor in Austin, Tx. and have been using the same plumber for eight years, and would like to continue to use him but he has thrown up his hands over a water hammer problem on a job where I am owed a substantial retainage, but the owners refuse to pay me until the hammer noise is resolved. This is a newly remolded bath with Grohe body spray valves and a temp. control valve. We ran new 3/4 inch hot and cold water lines to the bath and have strapped down new and existing lines. We have added arrestors at every valve, as well as custom air chambers. We finally added a pressure regulating valve on the yard line, but there was still a hammer at 45 psi., just no water pressure. Have any of you had any similar problems with Grohe valves, or can you recommend something else to try?

    • #289544

      More information would be helpful:
      What is the hot water temperature at the heater outlet? What is the temperature control valve setting? Is there a recirculator keeping the water line hot? A protective closing of the anti-scald feature can slam the supply valve shut making a water hammer. Does water flow to other taps also cause water hammer, or is the hammer only at the Grohe valves?

    • #289545

      Harold, thanks for the response. The temp is 126 degrees at the water heater and there is no recirculating pump installed. We are only having the hammer in the shower and occasionally in the adjacent grohe vanity faucets. There is not a hammer in any of the other valves in the house. We have checked all toilet seats and have cut off supply to all toilets, the hot and cold supplies to the dishwasher, the washing machine, all other sinks and still have the hammer. We have followed Grohe’s recommendation to change out the stems from ceramic to compression with no success. Does this help? Thanks, Robert.

    • #289546

      After some discussion, there is a reminder to remove the internals from the valves and flush them thoroughly. Little bits in the water line can lodge between the precision parts, making them require force to move, thereby making a hammer when they overcome the resistance and might score the internals. This is common in new construction.

      Water hammer requires a large body of water to move at high velocity agains a sudden restriction, so limiting the water flow to that required by the bathroom may also help reduce hammer. A balancing valve of a sort to restrict water flow to the combined amount of toilet, shower, and sink may limit the hammer potential.

      Long runs of tubing would do better to have a slight slope downward toward the fixtures. Air in lines would settle toward the inlet of the pipe run to be moved along with the water when it runs, instead of collecting at the fixture end to create bubble bounces as water follows a bubble to the valve mechanism.

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