Water Heater Anode Rod Size Gauge (Pocket Card)

A flat go/no-go card for sizing a residential water heater sacrificial anode before you order a replacement. Slide the rod body through the round holes and check the hex head in the hex cutouts. The smallest opening it fits is the size you need. Sizes included OpeningNominal (in)Designed hole (mm)* Round1/2″Ø13.00 Round5/8″Ø16.18 Round3/4″Ø19.35 Hex (across flats)1-1/16″27.29 AF Hex (across flats)1-1/8″28.88 AF *Each opening is +0.30 mm over nominal so a true-size part still slips through on a typical 0.4 mm nozzle FDM print. Verify with calipers after printing if you need lab-grade accuracy. Card size is 108 × 70 × 3.4 mm (2.8 mm plate + 0.6 mm raised labels), so it fits a 120 mm bed with room to spare. Rounded corners, keyring hole in one corner, raised labels — no supports. If rotten-egg hot water or a wet fitting at the top of the tank has you looking at the anode, start with the troubleshooting guides on https://waterheateranswers.com/. The same anode check applies to RV water heaters that smell of rotten eggs. How to use - Kill power / gas and cool the tank before opening any fitting. - Pull the old anode (hex at the top of most tanks, or behind a plastic plug). - Offer the rod body to the round holes — the smallest it slides through is your diameter. - Offer the hex head to the hex cutouts — match across-flats. - Order the matching rod (magnesium, aluminum, or aluminum/zinc depending on water chemistry).

Print settings - Orientation: flat on the bed as provided. No supports, no brim. - Layer height: 0.20 mm (0.16 mm makes the raised text sharper). - Perimeters: 3 · Top/bottom: 4 · Infill: 20–30% (gyroid or grid). - Nozzle: 0.4 mm. - Material: PETG preferred for a tool that lives in a damp closet; PLA is fine for a dry workshop. - Filament / time: ~16 cm³ (≈19 g PLA), under 45 minutes on most printers.

Tip: if a hole prints a hair tight, one light pass with a round file or sandpaper brings it to size. Do not scale XY if you care about the labeled sizes. License: CC BY 4.0