Over the weekend I changed out a lavatory drain. The old drain I removed had lots of old moldy putty and gunk that I cleaned up above and below, but some gunk was coming down from the overflow hole so I cleaned the outlet side of the overflow at the bottom of the sink bowl.

When I inserted the drain, something just occurred to me. I looked at the new drain overflow holes, and the sink's overflow hole, and I inserted the drain such that the two overflow holes are aligned with each other.

Is this something the pros do as a habit? Because I never even give it any thought on aligning the drain's overflow hole with the sink's overflow. The drains I came across always have two holes, and even if not aligned, there will be a partial opening, and we are not draining solids so it's just water rising too high spilling into it. But the gunk and hair got me thinking, that if they are aligned, than it is a wider hole and less of a chance of something getting caught in that pathway...or is this not something worth worrying about?

Thoughts?



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right or wrong.... i have never lined up the two openings.

i have taken out many and the gunk is not from water overflowing it is from the draining water laying around in the area.

lots of people ( self included) never fill the lave to overflow.

I also have never bothered lining up the openings, but it probably helps a bit.

Had a call from a customer about her bath sink only draining properly if the push stopper is unscrewed and removed. I have not been to the job yet but I suspect it is getting air-locked from slime buildup and air is not being vented through the sink overflow hole.

Most sinks with overflows are cast with a small reservoir at the bottom between the inner and outer shells, so that water can flow into the drain hole from any direction. As you have observed, over the years gunk can build up in there preventing water from escaping. DIY installers may inadvertently block the hole with putty or caulk. Once when we removed an older sink that had been disconnected for a long time, a few ounces of cloudy watery gunk dripped out of the bottom when we removed the waste pipe. It had been mouldering in there for years. You wear gloves, right?

I went to the job I mentioned previously. It was an acrylic cast sink and there was no chamber around the drain opening. The overflow passage had a small opening at the bottom, about 1/2 in wide and 3/8 in tall. Turned out it was not slime causing the airlock



Arrow shows the inlet(s) to the drain completely blocked by the body of the sink. Not surprisingly, the sink was getting air-locked and not draining well. I turned the drain assembly a bit so that the passages lined up and the sink drains well now.

They have five of these sinks in the house (large house) and only one had the passages lined up. I corrected the remaining four. This poor drainage had bugged the homeowners for years and they have had a couple of plumbers in over the years trying to resolve the issue. Makes you wonder if they were really plumbers.