The decision page is the rule. The elevation note is Bend wort pumps. These signs are sorted so you do not trim an impeller that was never the first fault.
Short version
Ranked by what the boiling table and the suction equation can show before any metal is cut. No placement was sold.
| Rank | Sign | What it means |
|---|---|---|
| 1 | Kettle far below 212°F | You may be on the 204–208°F rows |
| 2 | Curve drawn at 29.9 in Hg | 3,500 feet is published at 26.3 in Hg |
| 3 | Suction losses stacked on that gap | About four feet is only the air term |
| 4 | Flashing on the suction side | A discharge restriction is a different fault |
| 5 | Trim copied from sea level | Trim after the NPSH arithmetic, not before |
1. Read the kettle against the table
The USDA-adapted table is 212°F, 208°F, and 204°F at 0, 2,000, and 4,000 feet[1]. NOAA lists the Bend station at 1,115.6 meters[2]. If your thermometer matches a sea-level boil, believe the thermometer and check the elevation you wrote down. If it matches the high-elevation rows, stop using 212°F as the process target.
2. Look at the atmospheric term on the curve
One published table lists 29.921 inches of mercury at sea level and 26.326 inches at 3,500 feet, with boiling points 212.0°F and 205.7°F[3]. A curve that hides the atmospheric assumption is not a curve you can trust on this floor.
3. Add the piping you actually built
The four-foot gap is only the air. A long suction, a dirty strainer, and elbows add loss. NPSH available is atmosphere plus static head, minus vapor head, minus those losses. Write the four terms. A single “altitude derate” sticker is not the arithmetic.
4. Decide whether the flash is on the suction
Cavitation from low suction pressure marks the impeller inlet. A closed discharge valve is a different noise and a different repair. If you cannot tell them apart, say so on the callback. Guessing leads to a trim that does not touch the fault.
5. Trim only after the margin is known
Impeller trim is a capacity change. It is not required by a Deschutes ordinance found for this note. If NPSH available is already short, talk to the pump maker with the numbers. If a boiler shares the room, its permit is a separate file under OAR 918-225-0600[4].
How this ranking was made
Ordered from the published atmosphere inward to the metal. A trim recommendation that skips the boiling table is ranked last on purpose. No one paid for a position.
Questions a manager actually types
Q1. Is 205°F a measured kettle temperature?
It is an interpolation. USDA lists 208°F at 2,000 feet and 204°F at 4,000 feet. NOAA’s Bend station is at 1,115.6 meters, about 3,661 feet. A standard-atmosphere table lists 205.7°F at 3,500 feet. Measure your kettle. Use the table to decide whether 212°F was ever the right target.
Q2. Is four feet of lost suction exact?
It is arithmetic from 29.921 minus 26.326 inches of mercury at the 3,500-foot row, converted with mercury’s specific gravity of about 13.6. Call it about four feet of water and then measure your own suction losses. The table is not a survey of the pump pad.
Q3. Does trimming the impeller fix cavitation?
It might change NPSH required, and it cuts head. Recalculate available NPSH first. No Deschutes ordinance reviewed here requires a trim.
Q4. Where do I send the callback?
Use the rule page, and the Deschutes note if the floor is above 3,000 feet. The form still refuses a house and the places this desk does not take.
Go to the rule or the Deschutes note, then use the callback.
References
Accessed 9 October 2026 unless a page prints a later date.
- National Center for Home Food Preservation, boiling temperatures, from USDA AIB 539. nchfp.uga.edu.
- NOAA station GHCND:USC00350694. ncdc.noaa.gov.
- Snyder, boiling point and pressure table. ucfoodsafety.ucdavis.edu.
- OAR 918-225-0600. oregon.public.law.