If your reverse osmosis faucet has been dripping, or you notice a damp spot under the sink, the cause is usually one of a few simple things. This guide walks through a basic check you can do yourself in a St. Louis kitchen, what to look for, and when to call a licensed plumber.
Before you start
Know where your reverse osmosis system's shutoff valve is. Most setups have a small valve on the cold water line feeding the unit under the sink. Close it before you open any fittings. Keep a towel and a shallow bowl under the work area, and have a flashlight handy, because the space under most St. Louis kitchen sinks is tight and dim.
If your system has a storage tank, check its valve too. Shutting off the feed water does not always empty the tank, so expect a small amount of water when you disconnect tubing.
Where leaks usually start
- The faucet base and the threads where the faucet attaches to the sink or countertop
- Push-fit and compression fittings where the tubing meets the faucet, the storage tank, the drain saddle, or the filter housings
- The drain line connection, where waste water leaves the system
- Cracked or kinked plastic tubing, especially where it bends sharply behind cabinets
- Filter housing o-rings, which can weep when a housing is not seated fully
A simple check, step by step
- Dry everything with a paper towel so you can see where new moisture appears.
- Open the faucet slowly and let the system run through a fill cycle while you watch.
- Run a dry tissue along each fitting. Wet spots show where water is escaping, even when the drip is too slight to see.
- Look at the tubing for flat spots, cracks, or white crusting, which can mean a slow weep at a joint.
- Check the drain saddle and drain line. A slow trickle here can be normal in some systems, but a puddle or a leak at the joint is not.
Common fixes you can handle
Tighten a loose fitting
Many push-fit fittings are only partly seated. Turn off the feed valve, then open the faucet until the water stops to relieve the pressure. Push the tube firmly into the fitting until it bottoms out, and pull gently on it to confirm it is locked. Do not overtighten plastic threads, because that can crack them.
Replace a worn o-ring
Filter housing o-rings can dry out or pick up grit during a filter change. Remove the housing, wipe the seat clean, and check that the o-ring sits flat in its groove. Reseat it with a light coat of food-safe lubricant that the filter maker recommends for that housing.
Replace a cracked section of tubing
Cut the damaged section straight across with a tube cutter or a sharp blade, then push the new tube into the fitting. Make sure the replacement tube matches the size your system uses. Mismatched tubing is a common cause of repeat leaks.
When to stop and call a pro
Stop and call a licensed plumber if the leak comes from inside the storage tank, if the faucet base is loose and turning under the countertop, if water is reaching the cabinet floor from a joint you cannot reach, or if you see or smell signs of mold. Also get help if your St. Louis home has older galvanized or copper supply lines near the system, since a repair there can disturb fittings that are already weak.
Keep the area dry after you fix it
Wipe down the cabinet floor, then place a small dry paper towel on each joint overnight. Check the towels in the morning. Moisture left under a sink can stain wood, swell particleboard, and encourage mold, so a dry cabinet is part of the repair.
Next steps
Once the leak is stopped, write down the date and what you changed. If the problem returns, the same fitting is often the cause, and it may be time to have the whole run inspected. Keep your system's manual nearby so you know the correct tubing size and filter housing type before you order parts.