Why Water Line Connected to Sink Trap?

lrm11241September 17, 2013

While traveling in California, I noticed in the bathroom of my hotel that a water line came out of the wall (with no valve) and was connected to the P trap under the sink. This was the same type of supply line used for the hot and cold water service. The trap was made of metal. Please see attached photo.

I am unable to come up with a function for such a supply line between the wall and the trap, and I have been unable to find anyone who knows the function around where I live.

Does anyone know what this line would be for?

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It's called a water-prime and is required where there is a potential for the water present in the trap in normal use, evaporates due to a lack of use, IE.vacancy.

These are also found in floor drains.

The water in the trap serves the function of preventing the sewer gasses from migrating to fresh air.

    Bookmark   September 17, 2013 at 10:25PM
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Trap prime.
As mentioned above, used to keep the basin/tub/shower/floor drain trap water seals intact. Might be needed in arid areas with high heat, low humidity, high winds combined with marginal venting systems situations emptying traps, or combinations of similar conditions.

    Bookmark   September 17, 2013 at 10:44PM
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