Quick Answer:
If water upstairs feels slick, stay calm. First compare the hot tap upstairs with a hot tap downstairs to see if the issue is limited to the upstairs hot riser. If only the upstairs hot water is slick, the problem is likely in the upstairs hot supply line or its connection to the water heater rather than the whole house supply.
Why This Happens
- Contamination in a single hot riser: a build-up of oils, soaps or an unusual residue can end up concentrated in one branch of the system.
- Plumbing cross-connections or failed mixing valves that let soapy or oily fluids enter the hot line.
- Deposits or biofilm inside older pipes or a problem in a localized fixture supply.
- Recent work or products used near plumbing (cleaners, lubricants, or contractor materials) that can enter a riser if valves were left open.
Step-by-Step What to Do
1. Don’t use the water for drinking or cooking
Until you know what’s causing the slick feeling, avoid drinking the water or using it for food prep. Use bottled water or water from a confirmed-safe tap (for example, a cold downstairs tap if unaffected).
2. Compare upstairs and downstairs hot taps
- Turn on a hot tap in the upstairs bathroom and note the feel, smell, and appearance.
- Immediately check a hot tap on the ground floor or another level. Are both slick, or only upstairs?
- Also check cold taps on both levels—if cold water is clear and normal, that points to a hot-side issue.
3. Check multiple upstairs fixtures
- Try the upstairs shower, sink, and any other hot outlets. If all upstairs hot outlets are slick, the riser feeding that floor is the likely source.
- If only one fixture shows the problem, the issue may be local to that fixture or its supply tube.
4. Look for obvious sources
- Smell the water—if it smells like soap or detergent, that suggests a cleaning agent contamination; if it’s oily, consider nearby work or stored chemicals.
- If the slickness appeared after a service visit, ask the contractor what was done and whether any lubricants or products could have entered the lines.
5. Isolate the upstairs hot supply if you can
- If there is a shutoff valve that isolates the upstairs hot riser, close it to stop contaminated hot water from traveling to fixtures. Do this only if you can locate and operate the valve safely.
- If you cannot find an isolating valve or are unsure, stop using the hot water upstairs and proceed to call a professional.
6. Collect a sample and monitor
- Collect a small sample of the hot water in a clean container for a professional to examine if needed.
- After isolating the riser (if possible), briefly run downstream cold taps to confirm the rest of the house supply is fine.
7. Note related clues
- If the film feels oily, compare your situation to common cases like Oily residue after long vacation.
- If the water tastes like soap, see notes similar to Soapy taste in tap water.
What Not to Do
- Do not open upstairs walls before isolating risers. Disturbing walls or cutting into pipe runs can spread contamination, cause leaks, and create safety hazards.
- Do not pour home chemicals or bleach into the drains in an attempt to “clean” the supply—you can damage fixtures or create hazardous reactions.
- Do not assume the water heater is safe to dismantle yourself—leave internal work to a licensed plumber or technician.
When to Call a Professional
- Signs to call a plumber: the slickness persists after isolating the riser, multiple floors are affected, you cannot locate shutoff valves, or you notice strong odors or visible residues.
- Ask for a plumber who can trace the hot riser, test water samples, and check water heater and mixing valves. If contamination is suspected, request water testing.
- If anyone experiences skin irritation, nausea, or other health symptoms after exposure, seek medical advice and tell the plumber about the health concerns.
Safety Notes
- Wear gloves when handling suspect water samples or inspecting fixtures.
- Keep children and pets away from affected taps until the issue is resolved.
- Do not mix cleaning chemicals in the plumbing system. If the plumber suggests chemical treatment, follow their instructions exactly.
- If you shut off a riser, label valves so you and rescuers know which feed is isolated.
Common Homeowner Questions
- Is it safe to shower in slick hot water? No — avoid bathing until you know the cause; skin irritation or absorption of contaminants is possible.
- Could the water heater be the problem? Yes — deposits or backflow from the heater or a failing mixing valve can affect only the hot lines.
- Can I fix this myself? You can do basic checks (compare taps, locate shutoffs), but persistent contamination or if you can’t isolate the riser should prompt a professional call.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Oily Sheen, Slick Feel, or Soapy-Like Water.