Guides
Diagnostic plumbing guides: a symptom or a risk in, a fix or a part class out, with the code or standard cited by number.
Each guide starts from something you can see, hear or measure, and ends at the class of part or work that fixes it. The standard is cited by number, and the sizing or part page that follows is linked from the guide.
Water heaters 10 pages
Diagnose
Water heater blanket: worth it? DOE's 7% to 16%
DOE's 2017 guide: a tank warm to the touch can save 7% to 16% with a blanket, pipe wrap 3% to 4% more. A. O. Smith and an electric manual say newer tanks need none.
Diagnose
How to flush a tankless water heater by maker
Rinnai: 4 gallons of white vinegar for 1 hour. Rheem: no more than 2 gallons, 45 minutes. Noritz: 3-4 gallons, 1 hour. Navien: 45 minutes. Takagi prints none.
Diagnose
Water heater temperature: 120 or 140 F, and why
CPSC urges 120 F and prints 140 F as a 6-second burn; DOE puts the saving at 4% to 22% a year. Dishwashers without a booster are the exception, with a mixing valve.
Diagnose
Water heater leaking: where it comes from and fix
Five places a tank water heater leaks, from the T&P pipe to the tank itself. Makers say drips at the T&P pipe mean pressure over 80 psi; a tank leak means replace.
Diagnose
Water heater age from serial number: by brand
Rheem reads month then year (1209 = Dec 2009); A.O. Smith International and Lochinvar read year then week (2037 = week 37 of 2020); Bradford White uses letters.
Diagnose
Water heater pilot won't stay lit: thermocouple test
Bradford White's service manual: 10 millivolts closed-circuit keeps a thermocouple, 350 to 850 mV is a normal thermopile, two LED flashes is a weak pilot.
Diagnose
Water heater no hot water: electric and gas causes
Rheem lists 8 electric and 3 gas causes of no hot water. Upper element and ECO kill all of it; a lower element only shortens it. Press the reset once, never twice.
Diagnose
Water heater T&P valve dripping: causes and fix
A T&P relief valve opens at 150 psi or 210 F. A drip after each heating cycle is usually thermal expansion or supply pressure over 80 psi, not a bad valve.
Diagnose
Hot water takes too long: recirculation options
The wait is the cold water in the pipe: Type L copper holds 0.0251 gal per foot at 3/4 inch. Which of four recirculation options fits, and who should just insulate.
Diagnose
Water heater noises: popping, clicking, rumbling
Popping and rumbling are steam trapped under sediment: flush once a year, every 6 months on hard water (Rheem). Ticking or clicking is heat traps or pipe expansion.
Toilets, faucets and showers 5 pages
Diagnose
Shower head and faucet Black Friday deal check
Federal caps are 2.5 gpm for shower heads and 2.2 gpm for faucets; California prints 1.8. Check the cap, the cartridge family and the hole count before the sale.
Diagnose
Bidet Black Friday and Prime Day deal check
Black Friday is November 27, 2026. Before buying a bidet seat on sale: a GFCI outlet inside a 39 to 48 in cord, the right bowl, a 403 or 1273 W heater.
Diagnose
Will a bidet fit my toilet? 5 checks before buying
Bolt spread 5.5 in, round or elongated bowl, a reachable fill valve for the 7/8 in T-valve, a flexible supply hose, and a GFCI outlet within a 3.9 to 4 ft cord.
Diagnose
Which faucet cartridge do I have? Brand and clip
Find the brand first, then the retainer: Moen 1225 under a copper clip, 1255 under a nut, Delta RP50587 under a bonnet nut. Then take the old one with you.
Diagnose
Running toilet: the dye test that names the part
EPA's dye test: food coloring in the tank, color in the bowl after 10 minutes means the flapper. A running toilet wastes about 200 gallons a day.
Drains and disposals 4 pages
Diagnose
Garbage disposal leaking from bottom: find it
Most bottom drips start at the flange, dishwasher inlet or discharge gasket and run down. InSinkErator's newspaper test finds which; a housing leak is a call.
Diagnose
Toilet clogged: plunger vs auger, in order
Close the supply valve first. Korky says a toilet plunger clears a clog in 1 to 2 plunges; if not, a 3 ft toilet auger with a boot. Several slow fixtures: a plumber.
Diagnose
Slow drain: what to try first, in order
One slow fixture is a local clog: stopper, cup plunger over 4 inches of water, 25 inch barbed strip, 1/4 inch auger, then the P-trap. Several at once: a plumber.
Diagnose
Garbage disposal humming, not spinning: reset it
InSinkErator's fix: switch off, 1/4 inch Allen wrench in the bottom socket until it turns freely, cool up to 20 minutes, then press the red reset button.
Water pressure 3 pages
Diagnose
Water hammer: banging pipes and arrestors
A bang when water stops is water hammer, a pressure wave moving over 4,800 feet per second. The fix is an ASSE 1010 arrestor, AA size for a home fixture.
Diagnose
Do you need a thermal expansion tank?
IRC P2903.4.2 requires thermal expansion control where a check valve, backflow preventer or PRV closes the supply to a tank water heater. Open systems may not.
Diagnose
High water pressure: when 80 psi needs a PRV
Both model plumbing codes cap static pressure at 80 psi and require a pressure-reducing valve above it. A hose-bib gauge gives the number overnight.
Dehumidifiers 2 pages
Diagnose
Dehumidifier Black Friday deal check: 65 F rating
Black Friday is November 27, 2026. An old-test 70 pint label is 40 to 45 pints under the 2019 DOE test. Check IEF first.
Diagnose
Dehumidifier pints vs litres per day explained
US pints per day are tested at 65 F 60 % RH since 2019, UK/EU litres at 30 C 80 %, Japan litres at 27 C 60 % per 50/60 Hz. No source prints a conversion factor.
Leaks and shutoffs 2 pages
Diagnose
Sump pump not turning on: float switch or power?
Liberty, Zoeller and Wayne's troubleshooting tables: tripped GFCI, float pinned on the pit wall, piggyback plug, air lock (3/16 in vent hole), check valve backwards.
Diagnose
Washing machine hoses: replace every 3-5 years
IBHS says to replace washing machine supply hoses every 3 to 5 years and upgrade to braided stainless; 1 in 60 insured homes filed a water claim 2016-2020.
Pipes and freezing 2 pages
Diagnose
Burst pipe: what to do in the first ten minutes
Main valve first, at the meter or where the line enters the house. Then power off if it is safe, faucets open, photos, and no open flame on a frozen pipe.
Diagnose
What actually prevents frozen pipes
State Farm paid over $628 million on more than 20,000 frozen-pipe claims from 2024 through June 2025. The fix is pressure relief, not warmth.