Why is my reverse osmosis tank or system leaking?

Before you fix anything, turn the system off. The Pentek manual says to "turn off cold water supply to system at saddle valve," close the tank valve, and "open drinking water faucet to relieve water pressure." That leaves the tank shut in and the lines depressurized, so nothing keeps pushing water onto the cabinet floor. If the leak is a steady stream or is not from a spot listed here, the manual's advice is short: "shut off the water supply at the saddle valve, and close the tank valve," then call the manufacturer's technical support or a plumber.

Dry every joint with a paper towel. APEC suggests putting a paper towel under the system at installation to spot small leaks. The same trick helps now. A fresh damp spot on a dry towel shows exactly which joint is weeping.

### Between a filter housing and the manifold

This is the most common spot. Each filter housing seals with a rubber o-ring. Pentek says the o-ring must be "properly seated in the groove below the threads of the housing or a water leak could occur." Its repair steps are:

1. 1Remove the housing with the housing wrench.
2. 2Remove and clean the o-ring, and lubricate it with clean silicone grease.
3. 3Clean the groove below the threads "to remove any dirt or particles that may be preventing the o-ring from sealing completely."
4. 4Press the o-ring back into the groove and tighten the housing back onto the manifold, "HAND-TIGHTEN ONLY."

APEC's list adds two checks for housings: make sure the o-ring is present and not damaged, and look for a hairline crack in the housing. A cracked housing has to be replaced.

### At a push-in tube fitting

The blue, green or white tubes lock into quick-connect fittings. Pentek says "if tubing is not firmly connected, leaking will occur." To reseat one, close the tank valve and saddle valve, press the collar around the fitting, and pull the tube out. Then:

• Cut off 1 inch of tubing, cutting it squarely, and remove internal and external burrs.
• Mark the tube 5/8 inch from the end for 1/4-inch tubing, or 3/4 inch for 3/8-inch tubing.
• Push the tube in until the mark is flush with the fitting.

Watts describes the same fitting. The tube must go in "completely into the connector until it comes into contact with the internal tubing stop," and you should "pull on the tube to check that it is secure."

### At the storage tank valve

If the drip is where the valve screws onto the tank, Pentek's steps are to drain the tank through the faucet, remove the tube, unscrew the tank valve, put "two wraps of plumber tape on the threads of the storage tank," and thread the valve back on until snug. Then reseat the tube as above. APEC's guide gives the same cause: a loose connection or not enough tape at the tank ball valve. One caution comes from Watts. Its manual says "do not use Teflon tape with the Adapt-A-Valve," the supply connection, so tape goes only where your manual says.

### At the faucet

Two different problems show up here. If the faucet itself drips, APEC points to a loose screw under the lever, or a missing spigot o-ring. If water spills out of the small air gap on the faucet base, look at the drain tube. Pentek says the faucet's drain tube is "a gravity drain line," and that "any loops, kinks or sharp bends must be eliminated." A kinked line can send reject water "leaking through the air gap in the faucet onto the countertop and below the faucet." The manual also says to check for foreign matter in the drain line or at the drain clamp hole, and to check that the clamp and hole are aligned.

### At the drain saddle

The drain saddle is the clamp on the drain pipe that takes the system's waste water. APEC says a leak here "may be a result of missing adhesive sponge" and tells owners to contact the maker for a replacement. Where the saddle sits matters too. The Watts manual says it must be installed at least 1½ inches above the nut of the P-trap elbow "to ensure proper drainage." It also says not to install it downstream of a garbage disposal.

A tank that leaks is a different job. APEC says water leaking from the tank's pressure valve points to a ruptured bladder inside the tank, and it lists replacing the tank as the fix. That is not a repair to try on a pressurized tank. Our page on what to expect from an RO installation covers how the tank and lines are set up.

Do not assume a fix worked because it is dry in five minutes. Pentek says to check for leaks "after tank is fully pressurized (6-12 hours)." Watts says to check the system "frequently over the next 24 hours to ensure no leaks are present," and says the tank may take 3 to 6 hours to fill. Leave a dry paper towel under each joint overnight. If a leak persists, stop and get help.

Most of these leaks come from wear and handling, so a few habits help.

1. 1Change filters on schedule. Every filter change opens a housing, and a pinched or dirty o-ring is the usual cause of a new drip. Our page on RO filter replacement and maintenance gives the intervals.
2. 2Hand-tighten housings. The Pentek manual says "DO NOT OVER-TIGHTEN," which can distort the seal.
3. 3Keep the drain tube's path clear. Straight and downhill, with no loops.
4. 4Know your shutoff. Find the saddle valve and tank valve before you need them.
5. 5Check the cabinet. A quick look under the sink each month catches a slow leak before it damages the cabinet. Dry the cabinet floor and lay a paper towel under each joint, so the next drip shows up clearly. Our page on what to expect from an RO installation shows where each part sits.

If you cannot find the source, water is spreading, or the leak is at the supply saddle valve under the sink, call a plumber. HQ Plumbing & Air is licensed and insured, and can find and fix RO leaks. We offer free estimates and upfront pricing. If you are deciding whether a system is worth keeping, see whether reverse osmosis is worth it.