Fixture Supply Stop Replacement Standard

Purpose

A supply stop is the one valve in the house whose whole job is to be there in an emergency, and the one nobody tests until the emergency arrives. Replacing it has a peculiarity no other fixture repair has: the part you are removing is the part that would normally isolate the work, so the first decision is not about the stop at all, it is about where upstream you can shut off and whether that valve will actually hold. The second decision is the stub the new stop lands on, and that is what separates a twenty-minute job from an opened wall.

Scope

Covers replacement of angle and straight fixture supply stops on residential and light commercial water closets, lavatories, sinks, laundry boxes and appliance connections, on copper, chrome-plated copper, threaded iron or brass, CPVC and PEX stubs, through to the proved-shutoff test.

Does not cover main or branch shutoff valves, which the shutoff location and labeling SOP owns, or a stub that has to be re-run inside a wall, which becomes an access job. Fixture reconnection beyond the riser belongs to that fixture's own SOP.

Roles and responsibilities

Procedure

1. Find the upstream isolation and prove it before you touch the stop. Locate the branch or main shutoff, close it, then open the highest and lowest fixtures on that line. Acceptance: flow at the working fixture falls to nothing within about 60 seconds and stays dry with its handle open, with the isolation point written down. Wrong: assuming a main valve holds because it turned. Stop rule: a valve that passes water means you isolate further upstream or at the meter, and if nothing holds the job is rescheduled rather than started. Hazard: an old gate valve that has not moved in years can pack off or split when operated, so turn it slowly, keep your face out of line with the bonnet, and tell the customer before you turn it.

2. Drain the line down and confirm the stub is dead. Open the lowest fixture on the branch, then crack the riser nut at the stop and watch. Acceptance: no pressure behind the nut, and the drip stops rather than continuing at a steady rate. Wrong: a steady flow at the cracked nut, meaning the isolation from step 1 is not holding. Stop rule: re-close upstream and re-prove; do not continue on a line that is still fed. Hazard: on a hot stop the water at the stub can still be near tank temperature, and published scald data puts an adult burn at roughly five seconds at 140 F, so crack the nut with a rag over it and your hand behind, not below.

3. Read the stub before you take anything apart. Identify the material, measure the projection from the finished wall face, and look at the end of the tube for scoring, out-of-round and the position of the old compression ferrule. Acceptance: material, projection in inches, and end condition all recorded, and the projection compared against the minimum stub engagement in the new stop's instruction sheet, read off that sheet. Wrong: guessing that any stub takes any stop, which is how a chrome tube gets crushed by a nut sized for hard copper. Stop rule: a stub whose material you cannot positively identify does not get a stop chosen for it; call the lead rather than fitting a compression stop to an unknown plastic. Hazard: none, it is looking and measuring on a dead line, and it sits here because everything after it is hard to undo.

4. Remove the old stop without damaging the stub. Back the nut off while holding the stop body with a second wrench, then work the body straight off. Acceptance: the stop off, the stub straight, no twist marks and no collapsed section. Wrong: levering the body sideways, which bends a soft stub inside the wall where you cannot see the damage. Stop rule: a stub that turns in the wall stops the job, because the fitting behind it is moving. Hazard: the second wrench is not optional, since all the torque you apply goes into a fitting in a concealed wall cavity if nothing holds the body.

5. Prepare the stub, or stop and re-scope. Cut back past the old ferrule if there is length to spare, ream and deburr, and confirm the end is round. Acceptance: a clean, round, deburred end with projection still at or above the stop sheet's stated minimum after the cut. Wrong: leaving the old ferrule in place and stacking a new one behind it, which never seals. Stop rule: projection below the sheet's minimum after cutting means the stub is extended or the wall is opened, decided by the lead, and it is not solved by over-tightening. Hazard: never sweat a pre-1986 potable joint inside a closed vanity, since heating 50/50 tin-lead solder puts lead fume in your breathing zone in a confined space; a press or mechanical joint is the default, and any torch work means the cabinet doors open, ventilation to outside and the tech out of the plume.

6. Fit the new stop, matched to the stub and oriented for use. Slide the escutcheon, then the nut and a new ferrule, and make the joint up per the maker's instruction with the handle pointing where a person can reach it. Acceptance: quarter-turn ball type, lead-free marked for potable use, handle clear of the fixture and the cabinet, and the joint made up to the sheet rather than to feel. Wrong: reusing an old ferrule or over-torquing a compression nut on chrome tube until it necks. Stop rule: a nut that keeps turning without firming up means the ferrule is not seating and the joint comes apart rather than gets tightened. Hazard: a mechanical joint must remain accessible, so it does not get buried behind a fixed panel; only soldered, brazed and solvent-welded joints may be concealed.

7. Reconnect the riser and restore pressure slowly. Fit the riser to the fixture end, then open the upstream isolation a quarter turn and let the line fill before opening it fully. Acceptance: no weep at the stub joint, the stop body or the riser nut under a dry paper towel at ten minutes, with the fixture's own valve closed. Wrong: opening the main fast, which slams a fresh joint and can hammer a long run. Stop rule: any dampness at any of the three points means the joint comes apart and the ferrule is replaced, not nipped up. Hazard: this is the step that puts pressure back into a joint you just made, so open slowly, keep your face out of line with the stub, and stand where you can reach the upstream valve without crawling.

8. Prove the stop shuts off, then label it. Close the new stop and open the fixture fully for two minutes. Acceptance: flow at the fixture falls to nothing and stays there for the full two minutes with the fixture open, then the stop reopens fully and the fixture flows normally. Wrong: a thin stream that persists, which is a stop that will not isolate and is worse than none because the next person will trust it. Stop rule: a stop that passes water is replaced again on this visit, not left with a note. Hazard: none from the work itself, but tell the customer what you just proved and where the upstream isolation is, since that is the information they need at two in the morning.

The record this produces

Six fields, written before the tech leaves: the upstream isolation point used at step 1 and whether it held, the stub material and projection from step 3, the end condition after preparation at step 5, the stop model and connection type fitted, the ten-minute weep result from step 7, and the proved-shutoff result from step 8.

The upstream isolation field is the one that gets read by somebody standing in water. A shop that recorded "basement main, holds" has answered the next emergency call before it happens, and a shop that recorded "main passes, customer advised" has both a lead and a defensible position on why the next visit cost more. The stub fields do the ordinary work of getting the right stop on the truck the next time this fixture is touched.

One worked pass, including a failure

Powder room lavatory, chrome-plated copper stubs through a finished wall, cold stop weeping at the packing nut, customer wants both stops replaced.

Step 1 closes the basement main. Flow at the powder room falls to nothing in about 45 seconds and stays dry with the handle open, and the valve is recorded as holding. Step 2 opens a laundry tub at the low point, then cracks the riser nut: a short drip, then nothing.

Step 3 measures the cold stub at 1 1/4 in projection from the finished wall, with the old ferrule sitting about 1/2 in back from the end and a light score across the sealing area. The new stop's instruction sheet gives a 1 in minimum stub projection, read off that sheet.

Step 4 backs the old stop off with a second wrench on the body. The stub stays straight and does not turn in the wall.

Step 5 fails. Cutting back past the ferrule takes 1/2 in, and 1 1/4 minus 1/2 leaves 3/4 in of stub. That is 1/4 in under the 1 in minimum, so the stop rule applies and no stop is fitted to it. The lead approves an extension rather than a wall opening: the vanity back panel is removable, so the stub is extended with a press coupling and a short length of tube, no torch inside the cabinet and no heated pre-1986 joint. Re-measured, the prepared end projects 1 3/8 in, which clears the 1 in minimum by 3/8 in.

Step 6 fits quarter-turn lead-free ball stops on new ferrules, handles turned outward and clear of the vanity door. Step 7 refits the risers, opens the main a quarter turn, lets the line fill, then opens it fully. At ten minutes the paper towel at the stub joint, the stop body and the riser nut is dry on both sides.

Step 8 closes the cold stop and opens the faucet cold side fully. Flow stops and stays stopped for the full two minutes, then the stop reopens and the faucet flows normally. The hot side proves the same way. Both stops labeled, and the basement main recorded as the upstream isolation that held.

When the site does not match this procedure

Nothing upstream holds. Do not cut the stop. Restore what you can, put the finding in writing, and quote the main shutoff or the meter valve as its own job under the shutoff location and labeling SOP. A shop that starts anyway ends the day with a customer who has no water and no valve.

The stub is threaded iron and the threads are rotted. Unscrewing it risks breaking it inside the ell, which turns the job into a wall opening. Say that before you turn it, get the decision made in advance, and price the contingency rather than discovering it with the customer watching.

The customer asks for the old multi-turn stop to be repacked instead of replaced. Fit a new stop. A repacked stop with a hardened seat washer still fails to isolate, which is the exact failure step 8 exists to catch, and it will be your shop's name on it the next time it is needed.

References

• IPC and UPC provisions for accessible fixture shutoff valves and for concealed joints, in the edition your authority having jurisdiction has adopted; only soldered, brazed and solvent-welded joints may be concealed.
• NSF/ANSI 372 and the 0.25 percent weighted-average lead limit for wetted surfaces set by the Safe Drinking Water Act as amended in 2011, which is what the lead-free marking on the stop refers to.
• The stop manufacturer's instruction sheet, which is where the minimum stub projection and the make-up method for that connection type actually live.
• See related: the Plumbing shutoff location and labeling visit SOP, the Plumbing sink and faucet installation standard, and the Plumbing water hammer diagnosis and arrestor install SOP.