[bgs7]

I recently had 3 stone vessel sinks installed with grid drains. All three drain slowly while the faucet is running. As soon as I turn OFF the faucet or set it at little more than a trickle, the sink drains quickly. Bubbles seem to collect in the drain while the water is running causing the slow draining. I previously had no problem in any of these bathrooms with the former set-in sinks that had overflows. I am considering purchasing 3 flip top drains to replace the grids as there is more of an opening and, I am hoping, less of a chance for the air to get trapped. Any comments? Help! I have three beautiful nonfunctioning sinks!

[massplumber2008]

Here is what IAMGROWLER (onsite plumber) recently posted on this exact issue:

"Actually, the roll top drain is the best type of drain for a vessel sink; The roll top offers more drainage surface area than pop-up, grid, twist-n-turn or mushroom drains.

But still, the best way to drain a vessel sink is to use a glue type (ABS or PVC) p-trap and substitute the traps 90 for a Sanitary Tee -- Installing an AAV in the top of the Tee will substitute for the missing overflows venting action." Iamgrowler.

See picture below for roll top drain and for AAV pictures. An AAV is an air admittance valve that, in this case, may act to replace the missing overflow in your sink. The AAV needs to be installed 6 inches above drain line (not directly into drain as shown in pic.).

I would start by changing one grid drain to new roll type...see what happens. If no major improvement then I would go with an AAV and a new trap (as in pic). Then if that improved all...change out the rest.

Please keep us posted on result! Thank you... Mark

If this helped, please RATE THIS ANSWER.

[DaveGadgeteer]

Actually, an AAV goes in the wrong direction for this problem. The problem with these sinks is they need to let the air bubble between the sink and the liquid in the trap escape (surface tension makes the water plug the grid and trap the air in the vertical pipe). So you need a valve that lets air flow OUT freely (not IN under a vacuum, like an AAV), and you need to connect it anywhere between the drain pipe height and the sink drain grid. And you want the valve to close if liquid runs into it (e.g. if someone uses a plunger in the sink and the drain or trap is clogged). There are valves like this, automatic float valves, used for letting air bubbles out of solar water heater systems and hot water radiator heating systems, but they aren't optimized for this application. I'm working on using a ping pong ball inside some pipe fittings to do the job...