A shower that still leaks after a new cartridge usually has one of four problems: the cartridge is not fully seated or is turned wrong, debris or scale is left in the valve body, the replacement is the wrong series, or the cartridge was never the source. Match where it leaks to the cause, then reseat and flush.
Where is the water coming from?
The location tells you which fix to chase. Moen's PosiTemp leak guide lists the symptoms this way: a shower that "continues running or dripping with the handle in the off position," and water that leaks from the handle. For both, Moen's answer is to replace the 1222 cartridge. Which means that, when a fresh cartridge still drips, the work moves to the installation and the valve it sits in.
One symptom is not a cartridge problem at all. If the showerhead leaks only when you run the tub spout, Moen calls that stacking, and says it "is caused by either a restriction in the system or an installation issue." Skip the cartridge in that case and read the stacking section below.
What installation mistakes cause a leak after a new cartridge?
Seating and orientation come first. Moen's 1222 instructions for a PosiTemp valve give several details that are easy to miss:
- Make sure the H and C tab is pointing up when you slide the cartridge in, and "do not rotate the cartridge."
- The rubber ovals on the cartridge "are not permanently affixed and may fall off." If one slipped off during the install, the cartridge has no seal there.
- The H and C tab must be "flush with the valve body." If the retainer clip meets resistance, Moen says to check that the cartridge is flush with the valve body.
- Moen also says that if the retainer clip "cannot be installed for any reason or it appears to be damaged or broken, the water cannot be turned back on to the faucet" until the clip is replaced.
- Lubricate the surface of the oval rubber grommets before you install.
Delta's instructions for its 1300/1400 and 13/14 cartridges list a different set. Install it with the Hot Side wording on the hot water inlet side and press it into the valve body, "making sure the keys (8) are fully engaged with the slots of the body." Then reassemble the brass bonnet and slide the sleeve over the O-ring. One more catch applies to the 1300/1400 cartridge only: Delta says to "remove and throw away the black retention plug."
Brands differ on every one of these steps, so follow the instruction sheet for your own valve and not a general video. If you cannot tell the brand, our page on what type of Moen shower valve you have can help you place it.
Could it be the wrong cartridge?
It can be. Delta states that its cartridges are "not interchangeable," and gives a cap color test: a white cap means a 1300/1400 series cartridge, and a grey cap means a 13/14 MultiChoice. Check the cap color or the model number, or take the old cartridge with you to the counter, before you buy.
Is leftover debris or scale to blame?
It can be. Moen recommends cleaning and flushing the valve body when you install a new cartridge because that "eliminates any mineral build-up and loose debris that may have accumulated inside the valve body." The same article warns that "this debris could damage the new cartridge or obstruct the flow of water." Phoenix water is hard, with total hardness of 10 to 17.6 grains per gallon in the City's water quality report, so an old valve body here can hold a lot of scale.
Delta's instructions end with a flush: with the cartridge installed, "turn on water supplies," check for leaks, and "let supply lines flush for one minute without moving handle." Delta says that removes "any debris from the supply lines that can damage internal parts of the faucet and create leaks."
If you skipped the flush, the new seals may have been scored on their first day. Pull the cartridge, scrub the valve body with a soft nylon brush, flush it and reinstall.
What is a stacking leak?
If the showerhead drips while the tub spout is running, the new cartridge may be fine. Moen's troubleshooting page lists the installation checks:
- The tub spout may be blocked. Remove it, look for an obstruction, and replace the spout if it cannot be cleared.
- From the tub port of the valve, Moen says only "½" Copper or ½" Galvanized Iron pipe (IPS) can be used," so PEX or CPVC there needs to be replaced.
- The spout "can be no less than six inches and no greater than eleven inches below the valve."
- There should be only one elbow from the tub port to the spout.
- The valve body must not be installed upside down. Many valves have the word "up" on them.
Most of that lives inside the wall, so this is where a plumber comes in.
When should you call a licensed plumber?
Call if:
- the leak persists after you have reseated the cartridge, flushed the valve and confirmed the right part;
- you see a stain, soft drywall or damp tile near the shower, which can mean the valve body or a connection is leaking behind the wall (our page on leaking shower valves behind the wall lists the signs);
- you can see damage to the valve body itself, such as a crack;
- the problem looks like stacking, which involves piping.
HQ Plumbing and Air is licensed and insured, with free estimates and upfront pricing, and our residential plumbing team repairs and replaces shower valves. If the cartridge turns out to be stuck in the first place, start with why a shower cartridge will not come out.