Contractors, Drains, and Backflow Preventers, Oh my!

I was at a meeting today and there was a quick discussion about double check backflow preventers and reduced-pressure backflow preventers.  These devices prevent water from being sucked out of a piping system and contaminating it.  This is most commonly a concern when you're talking about connecting a potable (i.e. drinkable) water source to a device that will mix chemicals with that water (say a film developinig machine).  A comment was made by the contractor that only the reduced-pressure needs a floor drain.  This is partially true, as the reduced-pressure backflow preventer will 'spit' out of the bottom during operation and will need to be connected to a floor drain (typically via an air-gap fitting), but as an engineer I would want a floor drain under the double check as well for future maintenance.

A word of caution.  This was an experienced contractor with a lot of knowledge, but as a younger engineer I found it difficult to be able to tell whether I could take what a contractor would say for the truth.  My advice to you is to do your homework.  Take what you have been told and use it as a starting point to research your answer.  And of course for the young contractors the converse will also be true, the only difference lies in the responsibility of being right. 

Now my whole conversation centered around whether or not a drain had been shown on the plans and this is a great question.  Often times drains will not be shown or not shown in the correct locations for various reasons. Also drains may be located in places that will cause condensate or drain pipiing to cross a walking path, thus causing a tripping hazzard.  Or I have seen drains located half under a concrete house keeping pad.  So my advice to you is know what equipment needs a drain and review the location prior to bidding and again early in construction.

Comments

[WCD]

A floor drain for a RPZ is absolutely necessary, and it must be properly sized. Some of these valves can release several hundred gallons per minute when discharging.

[david jones]

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