Identify this supply tap

[Districtwolf10]

This tap is located in the water supply for my sink and washing machine. It has two holes in it that almost contantly percolates. The bottom line goes into the floor slab. Can't understand it's purpose. Pressure release? Trap primer?

 

[Stigster]

Could be to a backflow prevention device maybe? In the event of negative pressure in the supply pipework it will vent water to atmosphere instead of any potentially contaminated water being sucked back into the water main.]

For example - Someone puts a hose attachment onto the kitchen tap to wash out chickens or whatever. The end of the hose could be submerged in the chicken water. Then there is a pump failure at the water plant or someone cuts the pipe doing roadworks with a digger and then dirty water can be pulled from your sink back into the mains system. Not a good situation!

I believe that device is there to protect against such a scenario. I've not seen one of that exact design but I'm sure someone will be along to correct me if I've misidentified it.

 

[Chuck]

I think Stigster is probably right. It's also possible that it's a pressure relief valve. Is the supply a private pump that might need such protection?

 

[Districtwolf10]

I think Stigster is probably right. It's also possible that it's a pressure relief valve. Is the supply a private pump that might need such protection?

No, supply comes from the water utility. What puzzles me is why water is percolating in its opening. Is the water coming from the drain line? If so would it be hydrostatic Pressure? It hasn't rained in a while here and we aren't that close to the water table.

 

[Chuck]

No, supply comes from the water utility. What puzzles me is why water is percolating in its opening. Is the water coming from the drain line? If so would it be hydrostatic Pressure? It hasn't rained in a while here and we aren't that close to the water table.

Perhaps the valve is leaking slightly and the thin pipe that is supposed to take any leakage (or perhaps spillage when it is tested?) down and out through the wall has become blocked somewhere.

This is all just guesswork on my part (I'm having a coffee break from doing something very tedious and like puzzles!) I've never seen a valve exactly like yours in the wild. I associate Phillips with commercial rather than domestic installations. You'd probably need a local plumber familar with your local customs and practices to get a definitive answer as to why it's like is it.