Moen lifetime warranty -- use it first
Moen's limited lifetime warranty covers all mechanical defects, finish defects, and part failures for the life of the original purchaser. The easiest path to any Moen replacement part is a phone call or web chat to Moen customer service (1-800-289-6636) with the model number (printed on the showerhead body or original box). Moen ships replacement parts at no charge for covered claims. This should always be the first step before purchasing aftermarket parts.
Spray face and nozzle plate
Moen's Velocity and Engage showerheads have a replaceable spray face (the silicone nozzle disk on the face of the showerhead) that can be removed for cleaning or replacement. Mineral-clogged nozzles are the most common failure in hard water areas. Remove the spray face by unthreading or unclipping (varies by model -- refer to the included documentation), soak in a 1:1 white vinegar and water solution for 30-60 minutes, and reattach. If nozzles remain blocked, order a replacement spray face via Moen customer service by model number.
Handheld hose -- part 166323
The standard Moen handheld hose replacement is Moen part 166323 (60-inch, brushed nickel connection) and 166324 (chrome). This 1/2-inch ID hose with swivel ends fits all Magnetix and Engage handheld models. Hoses fail at the swivel connection after repeated flexing -- if the connection drips and re-tightening does not resolve it, replace the hose. Moen hose replacements are $18-$30 at retail and $10-$15 through direct warranty claim if within coverage period.
O-rings and washers
The most common drip point on a Moen showerhead is the connection washer -- the flat rubber washer seated inside the showerhead inlet that seals against the shower arm. This washer is $1-$3 at any hardware store (size: 5/8" OD, 3/8" ID flat rubber washer, standard plumbing supply). If the showerhead drips at the wall connection after installation, check this washer first before adding more Teflon tape. O-rings at the swivel joint (on adjustable and ball-joint showerheads) are also available from Moen customer service by model number.