Quick Answer:
Flexible supply lines can bulge, balloon, or kink when water pressure and temperature cycles weaken the hose material. Inspect any flex lines that look distorted and replace them with quality braided lines after you control pressure. Measure pressure peaks and address the pressure regulator and expansion tank to prevent the problem from returning.
Why This Happens
Flexible supply lines are often made from braided stainless or reinforced rubber. Over time, repeated pressure spikes and hot-water expansion stress the inner hose and connections. Heat plus pressure can soften hose material, allowing a section to expand (bulge) or kink. A partially closed or damaged valve at the supply stop can make the hose flex abnormally under pressure. If the home has high dynamic pressure or unchecked thermal expansion, the hose stays under strain and will deform more quickly.
You may also notice that High pressure causes noisy pipes or that High pressure breaking faucet cartridges becomes an issue in the same plumbing system—both are signs the pressure needs attention.
Step-by-Step What to Do
1. Shut off the water to the fixture
- Close the angle stop (shutoff) for the fixture. If there’s no local shutoff, turn off the main water supply.
- Open the faucet to relieve pressure and drain remaining water from the line.
2. Inspect the flexible supply lines
- Look for bulging, ballooning, soft spots, kinks, or twisting in the hose body.
- Check connections at both ends for seepage, corrosion, or loose fittings.
3. Replace warped or damaged lines with quality braided lines
- Remove the old flexible hose and install a stainless braided supply line sized for the fixture.
- Use good-quality fittings and hand-tighten, then give a quarter-turn with a wrench—don’t overtighten.
- Replace both ends if either connection shows wear.
4. Confirm angle stops are full open and operating
- Partially closed or damaged angle stops can pinch flow so the hose flexes unevenly. Fully open the angle stop and verify smooth flow.
- If an angle stop is stiff, leaking, or won’t fully open, replace it rather than forcing it.
5. Measure pressure peaks
- Attach a pressure gauge to a hose bib or washing machine connection and observe both steady pressure and pressure spikes when appliances run.
- Look for pressures consistently above 60 psi or sudden spikes; those are risk factors for hose deformation and can damage other fixtures.
6. Correct PRV settings and control thermal expansion
- If you have a pressure reducing valve (PRV), adjust it to a safe household pressure (typically 50–60 psi) or have a plumber set it correctly.
- Install or service an expansion tank if the pressure rises when the water heats—thermal expansion causes pressure peaks that deform hoses.
- After reducing pressure and fixing expansion, recheck hose condition and replace any that were warped.
7. Test and monitor
- Turn the water back on, check connections for leaks, and run hot and cold water to see if the replacement holds.
- Recheck pressure readings during normal appliance cycles to confirm spikes are controlled.
What Not to Do
- Don’t leave warped supply lines in place—they can fail suddenly; replace after controlling pressure.
- Don’t try to patch a bulging hose with tape, clamps, or temporary seals—these are unreliable and dangerous under pressure.
- Don’t ignore a partially closed or damaged angle stop; it can create abnormal stresses on the hose and fittings.
When to Call a Professional
- There is active leaking, visible corrosion, or you can’t isolate the shutoff for the fixture.
- Pressure readings show frequent spikes, the PRV needs replacement, or you need an expansion tank installed or sized correctly.
- You’re uncomfortable replacing lines or adjusting the PRV yourself—these are routine for a plumber and avoid mistakes that could cause floods.
Safety Notes
- Always shut off and relieve pressure before removing a supply line. Open the faucet to drain lines.
- Wear eye protection when loosening fittings; water can spray under pressure if a valve is not fully closed.
- If a line has already burst or is leaking heavily, turn off the main water supply and call a plumber immediately.
Common Homeowner Questions
- How fast should I replace a bulging supply line? Replace it as soon as possible after stopping the water and confirming pressure control.
- Can I use any braided line as a replacement? Use a certified stainless braided line sized for the fixture; avoid cheap rubber-only hoses.
- Will fixing the PRV stop this from happening again? Correcting the PRV and adding an expansion tank usually prevents repeat deformation if pressure was the cause.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see High Pressure Causing Fixture Damage.