PRV clogged by sediment

Quick Answer:

After a main flushing or nearby construction, loose sand and grit can enter the service line and lodge on a pressure-reducing valve (PRV) inlet screen or seat. Shut the water off, relieve the pressure, clean the inlet screen if the model allows, flush the supply through a tub spout or hose bib to clear remaining sediment, then re-test. Replace the PRV if the seat is visibly scored or leaks after cleaning.

Why This Happens

• City flushing, pipe repairs or nearby construction stir up rust, sand and mineral deposits that travel in the water main.
• That debris can collect on the PRV inlet screen or jam the valve seat, stopping the diaphragm from seating correctly and causing unstable or high downstream pressure.
• Small particles can score the metal seat so the valve won’t seal even after cleaning.
• Less commonly, a sudden rise in inlet pressure can push debris into the PRV; for related service changes see PRV failed after city pressure change.

Step-by-Step What to Do

1. Shut the water and relieve system pressure

• Close the main shutoff feeding the PRV.
• Open a downstream faucet (lowest and highest in the house) to drain pressure from the line and the PRV body.
• Confirm pressure is near zero on any downstream gauge before you open the PRV.

2. Inspect and remove the PRV cover

• With pressure relieved, remove the PRV bonnet or cover per the manufacturer’s instructions.
• Take note of spring and diaphragm orientation so you can reinstall exactly as found.

3. Remove and clean the inlet screen (if present)

• Many PRVs have a removable inlet screen or strainer. If yours does, remove it and rinse it thoroughly with clean water.
• Use a soft brush to dislodge trapped grit; do not use anything that will enlarge holes or damage the mesh.
• If the screen is corroded or torn, replace it before reinstalling the bonnet.

4. Check the seat for scoring and debris

• Inspect the valve seat and mating surface. Light sediment can be wiped away; scoring or deep marks mean the seat is damaged.
• If scoring is present the PRV may never seal reliably and should be replaced.

5. Reassemble and flush the line through a tub spout

• Reinstall the screen and bonnet, restore the inlet shutoff slowly, and open a tub spout or hose bib downstream to flush the line. This prevents sending loosened sediment into delicate fixtures.
• Flush until the water runs clear (several minutes may be needed after heavy sediment events).

6. Re-test regulation and monitor

• Close the tub spout, then check downstream pressure with a gauge. Adjust the PRV per the manufacturer if needed.
• Observe for a day or two to confirm stable pressure and no leaks. If pressure fluctuates or the valve drifts, replacement is likely required.

7. Replace the PRV if the seat is scored

• A scored or damaged seat usually cannot be repaired reliably in the field. Replace the PRV assembly to restore dependable pressure control.
• When replacing, install a new inlet strainer or screen to reduce repeat clogging and consider adding a serviceable strainer upstream if your plumbing allows.

What Not to Do

• Don’t flush sediment into delicate fixtures—use a tub spout or hose bib first.
• Don’t work on the PRV while the line is under pressure. That risks sudden water release and injury.
• Don’t attempt to grind or file a scored seat in place unless you have the exact replacement parts and factory guidance; improper repair can lead to leaks or failure.

When to Call a Professional

• Call a licensed plumber if you find a scored seat, if the PRV won’t adjust or seal after cleaning, or if you’re unsure how to relieve pressure safely.
• Also call if the PRV is hard-piped in a way that requires special tools to remove, or if repeated sediment events keep clogging the valve — a professional can assess upstream filtration or strainer options.

Safety Notes

• Always shut off the inlet and relieve downstream pressure before opening the PRV. Never assume pressure is gone without checking.
• Wear eye protection and gloves when working on plumbing to guard against sudden sprays and sharp debris.
• Be cautious of electrical equipment near work areas; water and electricity are a dangerous combination. Shut off power to nearby equipment if there’s any chance of flooding.

Common Homeowner Questions

• How long does cleaning usually take? 30–60 minutes for a basic inspection and screen clean; longer if you need to flush extensively or replace parts.
• Can I reuse a PRV after cleaning? Yes if the seat and internal parts are undamaged and the valve holds pressure; replace it if you find visible scoring or continued regulation issues.
• Will more frequent flushing help prevent this? Regular main flushing is outside homeowner control; installing a service strainer or sediment trap upstream can reduce the chance of debris entering your PRV.