Check installation of pop-up drain mechanism

Hey there, time traveller!
This article was published 12/06/2005 (7480 days ago), so information in it may no longer be current.

QUESTION — I am seeking your advice on a slow draining bathroom sink.

I installed a new bathroom sink with pop-up. The basin is a one-piece vanity top, made by General Marble, purchased at a local home centre. The hole for the water overflow is about the size of a quarter. As part of the installation I cleaned out the drain, therefore I know there is no blockage caused by material in the pipes.

My problem is that the basin is very slow draining and the problem seems to be caused by air in the drain. When the pop-up is first popped, water is forced back up the overflow. It can’t go down so it first comes up? If I lift the rubber seal of the pop-up with my finger the water bubbles with air as it slowly drains. Once the air is released it seems to drain somewhat better, but still slower than it should.

There is no leakage of water from the pipes inside the vanity. It all appears normal.

—Terry Schultz, e-mail

ACultured marble sink and countertop combinations units are very durable and generally good quality. They should be designed to drain properly, so the problems you are experiencing are either due to a defect in the plumbing drains or improper installation. I will suggest a couple of potential problem areas that should be checked.

The first place to start is with the “pop-up” mechanical drain mechanism. These mechanical drains will work effectively, but only if they are installed and adjusted correctly. Over 50 per cent of the homes that I inspect with these drains have the stoppers removed, due to homeowner ignorance for proper installation or simple laziness. The drain stopper is normally attached to a short metal rod that runs through and perpendicular to the drain, immediately below the sink. This rod is pulled up and down with another vertical rod that has a small knob or handle above the faucet. There is a clip or metal bar that connects these two rods together, and this is where many of the problems occur. These clips often slip on the rods or move during regular use and require periodic adjustment.

If the pop-up drain assembly is not properly adjusted below the drain, either the stopper will not fully seal at the sink or the opening to the sink drain hole will be too small to allow proper operation. This may be the main cause of your problem. If the stopper is not high enough above the sink when open, the water will not drain until there is sufficient room for the water to drain. This is partially due to the specific properties of liquids, which some may remember from school science class, but we will not go into that discussion, here. The simple solution is to stick your head under the sink and adjust the mechanism until you have the proper height of the stopper above the drain. This should be adjusted so that when open, it will allow good drainage, while still sealing the drain when closed. This may require a few trial-and-error settings, but should be an easy adjustment for most homeowners.

The other possibility is that there is not proper or adequate installation of the plumbing drains and vents. If the P-trap under the sink is not installed correctly or the connection to the drains behind the vanity is poorly done, this may cause poor drainage. I often see improperly installed “S-traps” or too many elbows and turns in drains under sinks, installed by home handymen or handywomen. There are often pamphlets available at home centres or Basic Plumbing books that show the proper conformation for a P-trap installation.

If the trap is installed correctly and the stopper height adjusted and the bubbling continues and water is still forced up the overflow in the sink, then inadequate venting is the likely culprit. Plumbing drains require venting to allow sufficient air into the pipes to push the water out. These vents should terminate above the roof of the home and the pipes may be completely or partially hidden by walls in the home. They may, however, be visible in the attic and the top exposed above the roof. Often these vents on the roof become plugged with debris such as leaves or ice and snow. A careful trip onto the roof of the home to inspect the top of the vent may be required. Any debris can be cleared, and better venting and draining should result.

If all of these items are checked and corrected and the problem persists, then a call to a licensed plumber may be the only solution. Unfortunately, the plumber may also have difficulty identifying a defect in the vents or drains if they are completely hidden inside the walls and attic, as is often the case.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the President of the Canadian Association of Home & Property Inspectors – Manitoba (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P. O. Box 69021, #110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358.

trainedeye@iname.com