How to fix a leaky bathtub faucet or a leaking shower knob

Why is my tub faucet leaking?

A spout that drips with everything off has a worn seal, water around the handle points to an O-ring or packing, and a spout that runs while the shower is on is the diverter. Before you buy anything, watch the faucet for a few minutes with the water off, then with it on. Where the water shows up tells you which part failed.

The last row is the one that costs real money. A drip you can see goes down the drain. A leak you cannot see goes into the wall or the floor.

What type of shower valve do you have?

Count the handles first: two or three usually means compression, and one means a cartridge or, on older showers, a ball valve. Compression valves have two or three handles, one each for hot and cold and sometimes a diverter in the middle. Each handle turns a threaded stem that screws down to press a rubber washer onto a brass seat. When the handle needs more and more force to stop the drip, the washer is worn. These are the cheapest to fix and the most forgiving.

Cartridge valves have one handle and a replaceable cartridge inside. On Moen single-handle showers, Moen's own repair articles give a simple test: a handle that only rotates is a Posi-Temp valve with a 1222 cartridge; a handle you pull out to start the water is a Moentrol or standard valve with a 1225. On Delta's Monitor 13 and 14 Series, the RP46074 (gray top) fits valves made after March 2006 and the RP19804 (white top) the older ones. Delta valves also seal against a pair of small rubber seats with springs behind them, sold as RP4993 for $8.08, and on a Delta that drips those are the first thing to replace.

Ball valves have one handle over a dome-shaped cap, with a slotted metal or plastic ball inside that rotates against rubber seats. They are older and less common on showers. The repair is the same idea as Delta's: new seats and springs, and a new ball if its surface is scored.

The part number is the whole job. Take the old cartridge or stem to the store with you, or read the number off it and order from the maker. Moen's repair pages treat the 1222 and 1225 as separate parts for separate valves, and one will not fit the other's valve.

A kitchen or bathroom sink faucet is a different fixture with its own parts; for those, see how to fix a dripping faucet.

What a dripping tub faucet costs a year

About 2,083 gallons and $38.58 a year at one drip a second, by the USGS drip count and New York City's 2026 water and sewer rate. Two federal sources give the drip rate. EPA WaterSense says a faucet dripping once a second can waste more than 3,000 gallons a year. The USGS counts 15,140 drips in a gallon, from a drip volume of a quarter milliliter measured on real faucets, which works out to 2,083 gallons a year at one drip per second. The EPA figure implies a bigger drip, about 10,512 to the gallon. I use the USGS count below because it states its assumption, and treat the EPA number as the upper case.

For price I use New York City's combined water and sewer rate effective July 1, 2026: $5.35 per 100 cubic feet for water plus sewer at 159% of that, $13.8565 per 100 cubic feet before rounding. A hundred cubic feet is 748.05 gallons, so that is $18.52 per 1,000 gallons. A drip is billed twice where sewer charges follow metered water, as they do there. Swap in your own utility's rate; the dollars scale in a straight line.

Now the payback. At one drip a second, the $6.99 washer pack pays for itself in about 2 months, the $33.64 Moen 1225 in about 10.5 months, and the $88.76 Moen 1222 in 2.3 years. At 10 drips a minute the 1222 takes 13.8 years, so the water bill alone will not justify it. What does justify fixing a slow drip is the rest: hot water you paid to heat (not counted here), mineral stains on the tub, and a handle you have to crank harder every month. Count the plumber, though, and a slow drip is rarely worth a $275 visit on its own. Fix it yourself or live with it until something else needs a plumber.

Parts and tools

Beyond those, a Phillips screwdriver, a hex key set, needle-nose pliers, an adjustable wrench, a flashlight, white vinegar for scale, and a rag in the drain so the small parts cannot go down it. A compression job on a recessed stem needs the socket set; an open wrench slips on the bonnet nut and rounds it. Cartridges often come with a plastic removal tool, and Moen's instructions use one.

How to fix a leaky bathtub faucet, step by step

Two- and three-handle compression valves

1. Shut off the water. Look behind the escutcheon for integral stops first, then use the house main. Check: the tub faucet opened fully gives nothing after a few seconds.
2. Pop off the handle cap, remove the screw and pull the handle, then unscrew the escutcheon and any sleeve. Check: you can see the hex of the bonnet nut on the stem.
3. Unscrew the stem with the right socket from the set, turning counterclockwise. Check: the stem comes out by hand once loose, with the washer on its end.
4. Replace the seat washer with an exact match from the assortment and a new brass screw; replace the stem packing or O-ring while it is out. Check: the new washer sits flat and fills the cup.
5. Look into the valve with the flashlight and feel the seat with a fingertip. If it is pitted or has a groove, unscrew it with the seat wrench and take it to the store to match. Check: the seat is smooth and round.
6. Grease the stem threads lightly and screw it back in. Check: the stem turns freely by hand until the last turn.
7. Turn the water back on, open and close the handle. Close it only until the water stops, with no extra crank. Check: no drip from the spout after one minute, and none after ten (my rule).

Moen single-handle cartridge (1222 or 1225)

1. Shut off the water and cover the drain. Remove the handle and escutcheon. Check: the retaining clip is visible at the top of the valve body.
2. Slide the clip out with needle-nose pliers. For a 1225 (Moentrol), first pull off the stop tube and the D washer, as Moen's article shows. Check: the clip is out and in a cup, not on the tub floor.
3. Turn the cartridge with the plastic twisting tool. For the 1222, Moen's article says slightly more than a quarter turn, with 45 degrees in parentheses, and the body bulges outward when it releases; for the 1225 it says a quarter turn (90 degrees). Then pull it out with pliers on the stem. Check: the cartridge is out and the valve bore has no pieces of the old rubber left in it.
4. Clean the bore and grease the new cartridge's seals. Insert it with the markings where Moen puts them: the H and C tab up on the 1222; plastic tabs at 12 and 6 o'clock on the 1225. Check: the cartridge sits flush with the valve body.
5. Put the clip back before any water goes on; Moen is explicit about this. Check: the clip slides fully home without forcing.
6. Turn the water on and test hot and cold. If they are reversed, Moen's articles explain how to rotate the stem 180 degrees. Check: hot is where you expect, and no drip after ten minutes.

Delta single-handle (Monitor 13 and 14 Series)

1. Shut off the water, remove the handle, escutcheon and bonnet nut. Check: the cartridge top is visible; note whether it is white (RP19804) or gray (RP46074).
2. Pull the cartridge straight out. Behind it, pick out the two rubber seats and springs with a small screwdriver. Check: the ports are clean and the new seats go in spring first, rubber facing out.
3. Install the new cartridge (if the old one is worn) in the same orientation, and the bonnet nut. Check: no drip after ten minutes, and the handle limit stop still holds the maximum temperature where it was.

When should you replace the valve instead of repairing it?

Replace the valve when the brass body itself is the problem: a seat that is cut into the body and cannot be unscrewed, threads stripped where the stem or bonnet goes, a crack, or a cartridge that will not come out even with the maker's puller. Replace it too when a multi-handle valve keeps eating washers every few months and you are tired of it. That is a different job, with a permit under 2021 IRC section R105.2 in towns that follow the model code, a new pressure-balancing or thermostatic valve under section P2708.4, and a way into the wall from behind. The tub and shower faucet replacement guide walks through it.

The cost jump is large. Angi puts a cartridge replacement at $275 on average and a valve replacement at $350 on average, with a typical top of $550 and a high end of $1,750 when tile is involved. So force is the wrong tool on a stuck cartridge. Heat the valve body with hot water, spray it with vinegar and wait, or buy the brand's cartridge puller. A cracked valve body turns a $34 repair into a valve job.

Mistakes that cost money

DIY or hire: the math

Plumbers earned a median $30.67 an hour in May 2025 (BLS OEWS, SOC 47-2152). Divided by 0.695, the wage share of compensation in private construction (BLS ECEC, June 2026), the loaded hour is $44.13. A cartridge swap is about an hour of a plumber's time, drive included, by my allowance.

By state, that loaded hour runs from $36.60 in Florida and $41.40 in Texas to $53.61 in New York and $69.14 in Illinois. Angi's $275 average sits well above every direct cost in the table, because a service call carries a trip, a minimum and the business behind the truck.

Do this one yourself. The parts are the same price either way, the tools cost less than $50 even if you buy the socket set, the seat wrench and the grease, and the worst likely outcome is a second trip to the store. Hire it when the stem or cartridge will not move, when the house main will not shut off, or when the leak is showing up somewhere you cannot see.