The kettle is not boiling at 212°F
You are moving wort in Deschutes County, above 3,000 feet, and the pump sounds wrong or the discharge pressure will not hold. The NOAA cooperative station at Bend is at 1,115.6 meters[1]. That is about 3,661 feet. The USDA boiling table gives 208°F at 2,000 feet and 204°F at 4,000 feet, against 212°F at sea level[2]. Your floor sits between those published rows. A sea-level pump curve still assumes the sea-level row.
- Nearest published boil at 3,500 feet on one standard-atmosphere table is 205.7°F.
- The atmospheric-head gap versus sea level is on the order of four feet of water.
- Impeller trim is not step one, and it is not a county ordinance.
The rule is physics, plus the vessel rule if you have a vessel
No section found in Deschutes County code for this note sets a wort-pump impeller diameter. Saying otherwise would be an invented ordinance. What is published is the station elevation and the boiling table. Net positive suction head available is atmospheric head, plus static head of the liquid, minus the vapor-pressure head of that liquid, minus the losses in the suction pipe. Atmospheric head is the term the elevation changes. A lower boil also means the wort is closer to its vapor pressure at a given “hot” reading that a sea-level brewer would still call subcooled.
A published table of standard atmosphere lists 29.921 inches of mercury and 212.0°F at sea level, and 26.326 inches of mercury and 205.7°F at 3,500 feet[3]. Subtract: 3.595 inches of mercury. Divide by 12 and multiply by 13.6, the specific gravity of mercury relative to water, and you get about 4.1 feet of water. Round it to about four feet and label it as table arithmetic, not as a survey of your brewhouse. Your gauge elevation, the weather that day, and the suction losses are still yours to measure.
If a boiler shares the room, it remains a Building Codes Division vessel. The operating permit comes first, under OAR 918-225-0600, and the inspection clock is yearly or every two years under OAR 918-225-0570 depending on power boiler versus low-pressure steam[4]. Altitude does not exempt the vessel. The vessel permit does not restore the four feet of atmospheric head.
If you skip the recalculation
The pump that was quiet at a sea-level factory acceptance test flashes in the eye of the impeller. You hear it, the discharge gauge hunts, and someone trims the impeller because trimming is a familiar repair. Trim without the NPSH arithmetic and you may quiet one symptom while giving away developed head you needed to reach the kettle or the fermenter. The skip is a repeated tear-down, not a citation this page can price, because Oregon has not published a fee for the study.
Who signs, who pays, how long
| Decision | Who | Document |
|---|---|---|
| Authorize the pump study | Brewhouse owner or the person who can stop the transfer | No county ordinance; the curve and the barometer |
| Accept a trim | Owner, after NPSH available is recalculated | Pump curve from the manufacturer, not a statute |
| Vessel permit, if any | Equipment owner | OAR 918-225-0600 |
| Inspection clock, if any | Division inspector | OAR 918-225-0570 |
| Study fee | Whatever the contractor writes | Not published by the state |
Why the Portland boiler page cannot be swapped in
Portland’s distinct measured fact is Bull Run hardness of 7 to 11 ppm and a municipal dose of sodium carbonate and carbon dioxide. The City of Bend tells its customers the tap water usually falls between 0.99 and 1.46 hardness units per gallon and calls that soft to slightly hard[5]. That Bend sentence is about drinking water. It does not move the boiling point. The sea-level row of the USDA table is the honest contrast: a Portland kettle is entitled to the 212°F row in a way a 3,661-foot floor is not. Paste the Bull Run dosing note onto this pump and the paragraph is false.
| Term | Deschutes floor | Sea-level row |
|---|---|---|
| Station elevation | 1,115.6 m at NOAA Bend | USDA table row at 0 feet |
| Boiling water | Between 208°F and 204°F; about 205.7°F at 3,500 feet | 212°F |
| Atmosphere | 26.326 in Hg at 3,500 feet on the cited table | 29.921 in Hg |
| First move | Recalculate NPSH available | Do not copy that recalculation downhill as if the air were the same |
Checklist for this pump
- Record the floor elevation you will stand on, not a ski-hill number and not the airport if the brewhouse is elsewhere.
- Read the kettle temperature against the USDA rows, not against 212°F.
- Write NPSH available with the local atmospheric head, static head, vapor head, and suction losses.
- Compare that figure to NPSH required on the pump curve at the flow you actually run.
- Only then talk about impeller trim, strainer, or pipe.
- If a vessel is in the room, pull its permit without pretending the permit fixes cavitation.
Fee and timeline
There is no published Oregon fee for an NPSH study or for impeller work. If the scope includes a boiler, the installation fee is $175 under ORS 480.595 and $196 on form 2502c, and the operating maxima are $110 or $55 by class[6]. Those dollars are vessel permits. They are not a pump price. The timeline that is published is the inspection interval for the vessel, not a delivery promise for a machined impeller. Weather changes barometric pressure around the table value. Recalculate on the day, or at least say which table row you used.
Questions a manager actually types
Q1. What temperature does water boil in Bend?
The USDA table adapted by the National Center for Home Food Preservation lists 212°F at sea level, 208°F at 2,000 feet, and 204°F at 4,000 feet. It does not print a 3,661-foot row. NOAA’s Bend station, GHCND:USC00350694, sits at 1,115.6 meters, about 3,661 feet, between those rows, so the boil is near 205°F rather than 212°F. A separate standard-atmosphere table lists 205.7°F at 3,500 feet. Use the nearest published row and say the station is a little higher. Do not invent a kettle survey the city has not published.
Q2. How many feet of pump suction does that elevation remove?
The same standard-atmosphere table lists 29.921 inches of mercury at sea level and 26.326 inches at 3,500 feet. The difference is about 3.6 inches of mercury. Mercury is about 13.6 times as dense as water, so 3.6 inches of mercury is roughly four feet of water column. That is atmospheric head you do not get to count. It is not a code minimum and it is not a promise about your suction piping. Elbows, a dirty strainer, and a high wort temperature take more margin on top of it.
Q3. Should the impeller be trimmed first?
No. Trimming can change the pump’s NPSH requirement at a given flow, and it also cuts the head the pump develops. Do the arithmetic for NPSH available at the local barometer first. If the available figure is already below the required figure on the curve, trimming is a conversation with the pump supplier, not the opening move. No Deschutes County ordinance reviewed for this note orders a trim.
Q4. Is Bend tap water the same problem as Bull Run?
No. The City of Bend describes its water as soft to slightly hard, about 0.99 to 1.46 hardness units per gallon, from the municipal watershed and the Deschutes regional aquifer. That is a water-treatment fact. This page exists because the kettle boils cooler and the pump sees less atmosphere. Portland’s 7 to 11 ppm Bull Run hardness does not explain a cavitating wort pump in Bend.
Q5. Does the boiler in the same room follow a different rule?
Yes. Cavitation is a pump problem. If a steam vessel sits beside the pump, OAR 918-225-0600 still requires an operating permit before that vessel runs, and OAR 918-225-0570 still sets the yearly or two-year inspection. The elevation does not cancel the vessel rule, and the vessel rule does not fix the pump.
Related
The three-machine split is on the rule.
References
Accessed 9 October 2026 unless a page prints a later date.
- NOAA NCEI. Station GHCND:USC00350694, Bend, OR, elevation 1,115.6 m. ncdc.noaa.gov.
- National Center for Home Food Preservation. Boiling temperatures by elevation, adapted from USDA Agriculture Information Bulletin No. 539, revised 2015. nchfp.uga.edu.
- Snyder, O. Peter. “Boiling Point / Atmospheric Pressure / Altitude,” table of standard temperature and pressure. University of California food-safety reprint. ucfoodsafety.ucdavis.edu.
- OAR 918-225-0600 and OAR 918-225-0570. Permits, schedules.
- City of Bend. Water quality, hardness range. bendoregon.gov.
- ORS 480.595 and BCD form 2502c. Statute, form.