Quick Answer:
If pressure drops only when you switch to the pull-out sprayer, the problem is usually a restriction or a faulty diverter inside the faucet, a partially closed supply valve, or an interaction with a connected appliance. Run targeted checks on the sprayer head, diverter, supply valves and nearby appliances before assuming a major plumbing failure.
Why This Happens
- Blocked spray head or inline filter: Mineral deposits or debris can restrict flow to the sprayer while the main spout still flows normally.
- Worn or stuck diverter valve: The diverter that routes water to the sprayer can fail or partially block flow, lowering pressure when the sprayer is selected.
- Partially closed/obstructed supply line or shutoff: A kinked hose or a valve that isn’t fully open limits total available flow to both spout and sprayer.
- Cross-connection with appliances: A dishwasher solenoid, ice maker supply, or a check valve issue can change flow dynamics when the sprayer is used. Check connected appliances and their valves.
- Venting and drainage effects: While venting problems typically affect drains, blocked air gaps or an improperly functioning air admittance valve near the sink can cause odd behavior worth checking.
- Cartridge or faucet-body restriction: Internal faucet parts can degrade or clog and reduce flow specifically under the sprayer load.
- Garbage disposal or drain back-pressure: In rare cases a drain blockage or disposal issue can make you notice different behavior when using the sprayer because you’re using the sink differently (running water at different rates).
Step-by-Step What to Do
1. Reproduce the problem and observe
- Run the regular spout and note pressure. Then switch to the sprayer and note how much it drops, whether it sputters, or if any noise appears.
- Try both hot and cold to see if one side is affected more than the other.
2. Check the sprayer head and hose
- Remove the sprayer head if possible and look for mineral scale or debris. Rinse or soak in vinegar if mineral deposits are visible.
- Stretch the hose fully and check for kinks or damage that could restrict flow.
3. Inspect the faucet diverter and cartridge
- With water off and supply shut, access the faucet body according to the manufacturer’s basic instructions and look for a stuck or worn diverter. Cleaning or replacing the diverter or cartridge often restores normal pressure to the sprayer.
4. Verify supply valves and lines
- Confirm the hot and cold shutoff valves under the sink are fully open.
- Look for crimps or bends in braided supply lines. If you have flexible lines to the sprayer, ensure they’re not pinched.
5. Isolate connected appliances
- Temporarily turn off the dishwasher and ice maker supply valves and test the sprayer again. Some solenoid valves or check valves can create a restriction when they share the line or piping layout.
- Check the dishwasher air gap or sink air gap for clogs that could affect flow behavior.
- Note: if you see discolored water after cycling an ice maker, that suggests a separate supply contamination issue—see the related note about water turns brown after ice maker.
6. Monitor venting and drainage behavior
- Listen for gurgling or slow draining which can indicate vent or drain issues. While not a direct cause of sprayer pressure loss, venting problems can reveal related system troubles.
- If you suspect a blocked roof vent, only inspect it safely or hire a pro; roof work can be hazardous.
7. Test under different flow conditions
- Open other fixtures in the house briefly to see if whole-house pressure changes when the sprayer runs—this helps distinguish a local faucet issue from a wider supply problem.
8. Replace small parts if comfortable
- If cleaning doesn’t help and you can access the diverter or cartridge, replacement parts are often inexpensive and straightforward to swap for a DIYer with basic tools and the right part number.
- If replacing parts doesn’t work or you find rusted fittings or hidden leaks, call a professional.
What Not to Do
- Do not force fittings or overtighten connections to “make it work.” That can crack fittings or strip threads.
- Do not use caustic drain chemicals to try to clear internal faucet parts or sprayer hoses—these chemicals can damage seals and finishes and are unlikely to reach the problem if it’s in the diverter or supply line.
- Do not ignore subtle early signs such as intermittent sputtering, minor drips, or fluctuating pressure—catching a failing diverter or clogged part early usually avoids bigger repairs.
When to Call a Professional
- If you isolate the problem to the faucet internals but aren’t comfortable disassembling it or can’t find replacement parts.
- If the pressure drop persists after checking the sprayer, diverter, and supply valves, or if multiple fixtures are affected—this can indicate a hidden supply-line blockage or a pressure regulator issue.
- If you find leaks, corroded fittings, or roof vent problems that require safe access and specialized tools.
Safety Notes
- Always shut off the sink supply valves before taking the faucet apart.
- Protect electrical appliances near the sink (dishwasher, garbage disposal) by unplugging or switching off power if you’re working under the sink.
- Do not climb onto the roof to check vents unless you have the right safety gear and experience—hire a pro for roof work.
Common Homeowner Questions
- Why does the pressure drop only with the sprayer?
A restricted spray head, a faulty diverter, or a partially closed supply is the most common cause. - Could the dishwasher or ice maker cause this?
Yes. Valves, air gaps, or solenoids on connected appliances can affect flow—check and isolate them during testing. - Can I fix it myself?
Often yes for cleaning or replacing a diverter or sprayer head; call a pro if the issue is hidden, involves the supply mains, or if you’re unsure.
Also watch for related issues like a Kitchen sink faucet drips after shutoff—small problems can point to broader faucet wear that’s easier to fix early.