# Trap seal primer



## Utakecare2019 (Aug 20, 2019)

sorry I am an architect but I have a plumbing question for engineers here
For sprinkler drain, when it dumps to a hub drain, gang drain, however you call it and then to the sewer line, many times a trap seal primer is added next to the sprinkler drain. 
How does this trap seal primer work? what is the purpose of it? 
I checked the video below which make sense. But for sprinkler condition, does not seem to work that way...




Thank you.


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## classicT (Aug 20, 2019)

A trap primer valve works by draining a small amount of water to a floor drain every time an adjacent fixture is used (typically a toilet). This minor amount of water is (should be anyway) of greater volume than the amount of water lost to evaporation. Thus, the trap remains full of water which blocks sewage gas from passing out of the floor drain.

As for your question, I am unsure as to where or how a floor drain and a sprinkler system would necessarily be intertwined. If taking the trap primer off a fixture line dedicated to a sprinkler system, you will have a problem because sprinklers do not run year round or with sufficient frequency. That is why trap primers are typically tied to flushometer toilet supply lines or other fixtures capable of pulling enough water to trigger a 10psi flux in line pressure.

And FYI, trap primers are good....trap seals are a whole different assembly and should typically be avoided.


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## north star (Aug 20, 2019)

*# ~ #*

There are alternatives to the "water type" Trap Primers......They are called
Trap Seals & Trap Guards, and are an approved product for use in floor
drains.

See this Link:  *http://www.josam.com/tsi-trap-seal-insert-waterless-trap-seal-floor-drains/*

and this one:* https://www.phwarehouse.com/products/Proset-#TG33%2dZURN-3"-Retrofit-Trap-Guard-Insert.html*

*# ~ #*


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## e hilton (Aug 20, 2019)

Assuming its ok to dump the sprinkler drain line into the floor drain ... and i assume that only happens once a year when the system is tested ...
I dont think there is any relationship between the sprinkler drain and the trap primer.  

A bit of trivia.  For older buildings that dont have trap primers, how do you keep the floor drains from drying out?  Float about a half cup of mineral oil on top of the water in the trap.  It doesnt evaporate, and will simply gets washed away if there is ever a flood.


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