Plumbing and Gas

Tools in this group

• Pipe Sizing - Water supply by fixture units; drainage by DFU.
• Friction Loss - Hazen-Williams for water; Darcy-Weisbach for gas.
• Pipe Volume - Gallons per foot by diameter.
• Pump Sizing - Required head and flow.
• Static Pressure Loss in Piping - Static pressure loss along a pipe run.
• Gas Pipe Sizing - BTU capacity by pipe size, length, gas type.
• Drainage Slope - 1/4 inch per foot rule and variants.
• Pressure Conversion - PSI, head feet, inches of water column, kPa, bar.
• Backflow Reference - Common backflow scenarios and preventer types.
• Water Hammer Arrestor Sizing - PDI WH-201 designation from total fixture units.
• Hot Water Recirc Pump Head - Pump head from pipe length, fittings, target flow.
• Hot Water Recirc Loop Sizing (ASPE) - Per ASPE Data Book Vol. 4 Ch. 6: derives heat-loss rate, required GPM from set-point delta, friction head via Hazen-Williams, and recommended pump size from loop length / pipe size / insulation / temperatures. ASHRAE 90.1-2022 §7.4.4 governs recirc control.
• Septic Tank Sizing - Minimum tank gallons from bedrooms or daily flow.
• Trap Arm Length - Maximum trap arm length by pipe diameter and slope.
• Pipe Thermal Expansion - Linear expansion (in) for copper, PEX, PVC, CPVC, steel.
• Tankless Water Heater GPM - Achievable flow from burner kBTU and inlet/outlet temperatures.
• Gas Leak Rate (Orifice) - Estimated leak rate from orifice diameter and upstream pressure.
• Stormwater Rational Method - Q = C * i * A peak runoff in cfs and gpm with bundled C values.
• Manning's Equation Drainage Slope - Self-cleansing slope and slope to carry target flow at half-full.
• Drainage Invert Elevation, Drop, and Cover - Invert-out, total fall, and cover over a gravity run from its slope and length.
• Hydronic Radiant Floor Loop Sizing - The tube footage from the heated area and on-center spacing, the loop count against the per-loop length limit so no loop exceeds the head the manifold can push, and the design flow per loop from the room load: tube = area x 12 / spacing, loops = ceil(tube / max loop), GPM = load / (500 x delta-T) (300 ft^2 at 6 in o.c., 9,000 Btu/hr -> 600 ft, 2 loops, 0.45 GPM per loop). The manufacturer's tubing tables and the room-by-room heat loss govern the final layout; this sizes footage, loops, and flow from a uniform load, not the panel surface-temperature design.
• Hydrostatic Test Pressure and Hold - Test pressure (1.5x water / 1.25x gas) and recommended hold time.
• Grease Trap Sizing - Volume from peak flow, retention, and loading factor; PDI G101 cited.
• Glycol Freeze Protection Mix - Glycol percent and concentrate gallons from manufacturer freeze-point curves.
• Hydronic Expansion Tank - Required diaphragm tank volume from system volume, fill, and relief pressures.
• Backflow Preventer Pressure Loss - Pressure loss interpolated from manufacturer-published curves.
• Water Hammer Pressure Surge (Joukowsky) - Wave celerity from pipe-fluid coupling, pressure surge dP = rho × a × dV, and rapid-closure flag against 2L/a.
• Pump Operating Point - Intersection of bundled pump curve with H_sys = H_static + k Q^2; SVG plot + numeric table at sample flows.
• Septic Drainfield Trench Length - Required absorption area and trench linear feet from design daily flow and the application rate set by your local code.
• Pipe Thermal Expansion and Loop Sizing - Linear expansion plus the guided-cantilever expansion-loop leg L_loop = sqrt(3 × E × D × dL / S_a).
• Water Heater Recovery Rate - Recovery gph and AHRI first-hour rating from input rating, efficiency, and temperature rise. gph = input BTU/hr x efficiency / (8.33 x delta-T). Per DOE 10 CFR 430 / AHRI 1300.
• Water Heater Thermal Expansion Tank - Potable closed-system expansion volume and required tank size from heater capacity, temperatures, and incoming pressure. Per ASPE PEDH Ch. 6 / ASME B40.1 steam tables; IPC 604.8 PRV note.
• Sanitary Drain DFU Sizing - Total drainage fixture units from a fixture list and the minimum pipe size for a horizontal branch, vertical stack, or building drain. Per IPC 2021 §710 with Table 709.1 DFU values.
• Trap Primer Sizing - Primer / distribution-unit count, annual water use, and an IPC 1002.4 occupied-space compliance check for floor-drain trap seals. Manufacturer flow rates govern.
• Backflow Assembly Sizing Screen - Hazard-driven assembly selection (RP required for any high / health hazard per IPC 312), head loss at design flow from the bundled assembly curves, the pressure remaining downstream, and the EPA 40 CFR 141.85 / AWWA M14 annual-test reminder.
• Cross-Connection Air Gap (IPC 608.15.1) - The minimum air gap for the most positive backflow protection there is -- the physical gap between a supply outlet and the flood-level rim, which nothing mechanical can defeat. IPC 608.15.1: the gap is twice the effective opening diameter but never less than 1 in, and three times the opening within three diameters of a wall. A 1 in opening needs a 2 in gap (3 in near a wall); a 1/2 in opening computes 1 in where the absolute minimum governs. Checks a measured installed gap against the requirement. For indirect-waste and tank-fill protection. A design aid, not a substitute for the plumbing code adopted by your AHJ.
• Hydronic Fill Pressure (Static Height) - The cold-fill make-up pressure a hydronic (hot-water heating) loop needs to lift water to its highest point and keep it above atmospheric so air is not drawn in and the pump does not cavitate. fill = height / 2.31 + margin (2.31 ft of water = 1 psi), a common margin about 4 psi. A 30 ft system needs 17.0 psi (leaving 4 psi at the top); a 35 ft system needs 19.2 psi -- each story adds about 4.3 psi of static lift. Set the automatic fill valve and expansion-tank pre-charge to this; the relief valve sits well above. A design aid; the manufacturer's instructions govern.
• Trap-Seal Protection Check - Within-limit pass/fail and percent of the permitted trap-to-vent distance used, with a self-/induced-siphonage flag when the vent is inadequate. Per IPC §1002 / UPC §1002; the permitted maximum is user-supplied from the adopted table.
• Water Meter Sizing from Peak Demand - Adequate/undersized verdict, percent of the meter's normal-flow rating used, and the headroom. Per AWWA M22 and the C700-series; meter flow ranges are user-supplied for the candidate size.
• Water Thermal-Expansion Volume - Expanded water volume gained on heating from bundled NIST water-density points, the expansion as a percent of system volume, and a closed-system expansion-control note.
• DWV Vent-Stack DFU / Length Check - Pass/fail of a vent stack against the adopted code's permitted DFU and developed-length table values, the percent of length used, the remaining margin, and a vent-at-least-half-drain check.
• Low-Pressure Fuel-Gas Pressure Drop (Spitzglass) - Pressure drop (in. w.c.) and velocity for low-pressure fuel gas via the Spitzglass equation, with a flag when the drop exceeds the low-pressure validity range.
• Septic Pump / Dose Tank Volume - Net dose per cycle, pumped volume per cycle and per day, and the dose-to-void ratio for a timed-dose pressure-distribution field. Per the USEPA Onsite Wastewater Treatment Systems Manual; the dose count and float settings on the permit drawing govern.
• Septic Tank Pump-Out Interval - Years between tank pump-outs from the working volume, household size, and a per-capita sludge/scum accumulation rate. A planning estimate -- a sludge-judge measurement and any mandatory state interval govern.
• Septic LPP Orifice Flow and Squirt Height - Per-orifice flow, total orifice count, and system flow for a low-pressure-pipe or mound distribution lateral via the orifice-discharge equation. Orifice size, spacing, and layout come from the permitted onsite design.
• Mixing / Tempering Valve Blend Temperature - Blended delivery temperature, mix ratio, or hot flow for a tempering valve, with a scald-limit flag.
• Well Pressure-Tank Drawdown and Sizing - Usable drawdown, runtime per cycle, and short-cycle flag (or the required tank size) from cut-in/cut-out and precharge by Boyle's law.
• Pipe Velocity and Erosion Check - Flow velocity (v = 0.4085*gpm/d^2) and the copper erosion-corrosion verdict, or the max flow for a velocity ceiling.
• Probable Peak Demand (WSFU to GPM) - Hunter's-curve probable peak flow in GPM from total water-supply fixture units, for flush-tank or flush-valve systems.
• Water-Supply Pressure Budget - Available residual at the critical fixture after elevation, meter, backflow, and friction losses, with a go/no-go verdict.
• Roof Drain and Leader Sizing - Storm flow in GPM from roof area and design rainfall, then the vertical leader and sloped horizontal storm-drain size from IPC capacity tables.
• Overflow Scupper Sizing (Weir Flow) - Secondary (overflow) scupper as a rectangular weir: Q = 3.33 L H^1.5 (cfs, feet), contracted 3.33(L - 0.2H)H^1.5. A 6 in scupper at 3.5 in head passes 118 gpm (104 contracted); a wide 12 in / 2 in scupper passes 102 gpm. Head is at the blocked-primary condition (IPC 1108 / FM Global). The code and roof-loading check govern.
• Sewage Force-Main Scour Velocity - V = 0.4085 Q / d^2 (ft/s, gpm, in), vs the ~2 ft/s minimum scour to keep solids suspended. 50 GPM in a 2 in main -> 5.11 ft/s (scours); the largest ID still holding 2 ft/s is 3.20 in, so a 4 in main (1.28 ft/s) lets solids settle. Ten States Standards; the state criteria and pump curve govern.
• Stormwater Detention Volume (Modified Rational) - Q_in = C i A, storage = (Q_in - Q_allow) x duration x 60. C 0.85, i 3 in/hr, 2 ac, Q_allow 1.0 cfs, 30 min -> 5.10 cfs in, 7,380 ft^3 (0.169 acre-ft); a longer 60 min / 2 in/hr storm needs 8,640 ft^3, so the critical duration must be searched. The routing and outlet govern.
• Sump / Ejector Basin Drawdown and Cycle Check - Drawdown volume, run and fill times, cycles per hour, and a short-cycle verdict for a sump or sewage-ejector basin against its inflow and pump rate.
• Gas Appliance Connected Load (CFH) - Total connected BTU/hr from an appliance schedule and the cubic-feet-per-hour demand for natural gas or propane that feeds gas-pipe sizing.
• Water-Heater T&P Relief and Discharge - Checks the T&P relief valve's rating against the heater input and reports the IPC 504.6 discharge-pipe size and requirements.
• Pipe Hanger Spacing and Count - Maximum support spacing for a pipe material, size, and orientation from IPC 308.5, and the hanger count for a run.
• Water Softener Sizing - Compensated hardness, daily grain load, days between regenerations, and salt per regen and per year for a water softener.
• Pipe Cold Spring (Cut-Short) - Free thermal growth, the cold-spring gap to cut the run short, and residual movement for a pipe sprung into place at install temperature (ASME B31.1 §119).
• Time of Concentration (Kirpich) - The storm duration stormwater-rational needs but never computes: the Kirpich estimate tc = 0.0078 L^0.77 S^(-0.385) (tc min, L ft, S ft/ft) - the time for runoff to reach the outlet, the duration at which a designer reads the design rainfall intensity off the local IDF curve. A 1,000 ft flow path at 2% slope gives 7.2 min; flatten it to 0.5% and the water takes 12.3 min, a lower intensity and a smaller peak - the flood-control value of grading a site flat. Single-segment estimate, not the TR-55 three-segment sum. A design aid; the engineer of record governs.
• Orifice Discharge Flow - The flow through a sharp-edged hole that sizes a detention-pond outlet, a tank drain, or a restrictor plate: Q = Cd A sqrt(2 g h), Cd about 0.6 sharp-edged, head to the orifice center. A 6 in orifice under a 4 ft head sheds 1.89 cfs (849 gpm); the flow scales with the square root of the head, so a 2.25x head raises it only 1.5x - the gentle stage-discharge control that holds a post-development peak to the pre-development rate. Free/submerged, steady head, small orifice; the falling-head time-to-drain is separate. A design aid; the engineer of record governs.
• Tank Drain Time (Falling-Head Orifice) - How long a tank takes to empty through an orifice, integrating the falling head the steady orifice tile leaves out: t = 2 A_t (sqrt(h1) - sqrt(h2)) / (Cd A_o sqrt(2 g)) for a constant-cross-section tank. A 100 ft^2 tank draining a 6 in orifice empties from 9 ft in 10.6 min, but reaches the last foot in only 7.1 - the flow slows as sqrt(h), so the final foot alone takes another 3.5 minutes. Prismatic tank, free discharge, steady Cd (~0.6). A design aid; the engineer of record governs.
• Open-Channel Froude Number, Regime, and Critical Depth - Whether an open channel runs tranquil or rapid, which manning-slope and weir-flow never tell you: Fr = V/sqrt(g D) classifies the regime (Fr < 1 subcritical / downstream-controlled, Fr > 1 supercritical / upstream-controlled), and the rectangular critical depth yc = (q^2/g)^(1/3) confirms it. A 4 ft channel at 50 cfs and 2 ft deep runs Fr 0.78 subcritical (yc 1.69 < 2 ft); drop the depth to 1 ft and Fr 2.2 supercritical - the same channel, the setup for a hydraulic jump. Rectangular section; normal depth and the jump are separate. A design aid; the engineer of record governs.
• Hydraulic Jump: Sequent Depth and Energy Loss - Where supercritical flow leaps to a deeper tranquil depth below a chute or culvert, the jump the Froude tile only sets up: Belanger's sequent depth y2 = (y1/2)(sqrt(1 + 8 Fr1^2) - 1) and the specific-energy loss dE = (y2 - y1)^3/(4 y1 y2). A 10 ft channel at 100 cfs and a shooting 0.8 ft depth (Fr1 2.46) jumps to 2.42 ft and throws away 0.55 ft of head; push it to 200 cfs (Fr1 4.93) and it jumps to 5.19 ft killing 5.1 ft - which is why a stilling basin is sized to the Froude number, not the flow. Rectangular, horizontal channel; the tailwater must supply the sequent depth. A design aid; the engineer of record governs.
• Velocity Head and Dynamic Pressure - Velocity head h_v = V^2/(2g) (ft of fluid) and dynamic pressure q = 1/2 rho V^2, both scaling with V^2. Water at 10 ft/s -> 1.55 ft head, 0.67 psi; at 20 ft/s -> 6.21 ft, 2.69 psi (four times for double the velocity). Why a small velocity increase drives large minor losses. The code velocity limits govern.
• Flow Continuity Velocity at a Size Change - Continuity V2 = V1 (D1/D2)^2 from Q = A V constant. Water at 6 ft/s reduced 4 in to 2 in jumps to 24 ft/s (past the erosion limit); only to 3 in gives a gentler 10.7 ft/s. Expanding slows the flow and recovers pressure. Incompressible full flow. The code velocity limits govern.
• Bernoulli Total Head (Pressure + Velocity + Elevation) - Total head H = P/gamma + V^2/(2g) + z (ft of fluid), the mechanical energy per unit weight, conserved along a streamline with no loss. Water at 30 psi, 6 ft/s, 10 ft -> 69.23 + 0.56 + 10 = 79.79 ft; where velocity drops the head converts to pressure (Venturi). The engineer of record governs.
• Thrust Block Bearing Area at a Pipe Bend (AWWA M41) - Resultant thrust at a bend T = 2 P A sin(theta/2) and the bearing face Ab = T / (allowable soil bearing), AWWA M41. An 8 in main (OD 8.625), 100 psi, 90-degree bend, 2000 psf soil -> T 8,263 lb, Ab 4.13 ft^2; a 45-degree bend halves the thrust (the sin(theta/2) term). Use the test/surge pressure. A design aid; the engineer of record governs.
• Water Main Chlorination Dose - The chlorine to charge a newly installed or repaired water main the AWWA C651 way: pipe volume, the pounds of available chlorine for the dose, and the product weight at its strength. Flush and pass a bacteriological test before return to service.
• Well Shock-Chlorination Dose - The household bleach to shock-chlorinate a private well from the casing diameter and standing water column: well volume, the available chlorine for the target ppm, and the bleach to pour in. The local health department governs the procedure and clearance.
• High-Altitude Appliance Input Derate - The derated maximum input for a gas appliance at altitude per the NFPA 54 / IFGC high-altitude provision: from the nameplate input and installation elevation, the derate factor (default 4% per 1000 ft above 2000 ft, both editable) and the derated input, with a high-altitude-kit flag. Field orifice drilling is generally prohibited; use a listed kit and the AHJ governs.
• Natural-Gas / Propane Conversion (Input and Orifice) - What changes when an appliance is converted between natural gas and propane: the required volumetric flow for each fuel at the same input (cfh = input / heating value) and the orifice-area ratio from first-principles orifice flow (Q proportional to area x sqrt(pressure / specific gravity)). Field orifice drilling is generally prohibited; install the listed manufacturer conversion kit.
• Medical Gas System Demand and Diversity (NFPA 99) - The first sizing step for an oxygen, medical-air, nitrous, or vacuum main: connected flow = station (outlet/inlet) count x per-station design flow, and the system design flow = connected x a diversity (simultaneous-use) factor that falls as the station count rises. 20 oxygen outlets at 1.0 scfm with diversity 0.25 give a 5.0 scfm design flow; medical-surgical vacuum's higher simultaneous use (0.50) drives a larger design flow per inlet. The per-station flows and diversity factors are read from the adopted NFPA 99 edition and the facility's equipment list (user-supplied here); medical-gas piping is installed and certified by brazing-qualified plumbers and pipefitters (ASSE 6010), and a medical-gas verifier and the AHJ govern. This feeds pipe sizing, not the system design itself.
• Storage Water-Heater Sizing (First-Hour Rating) - Whether a storage water heater meets the household peak-hour demand: the first-hour rating (FHR) is the usable storage plus one hour of recovery, with recovery = input x efficiency / (8.33 x rise), checked against the peak-hour draw. The manufacturer's rated FHR on the EnergyGuide label governs the final selection; this is a sizing check, not the rating.
• Flash Steam Percentage Across a Pressure Drop - The fraction of condensate that re-boils to steam when it drops across a trap from a high pressure to a lower one: flash = (hf_high - hf_low) / hfg_low, from the saturated-water enthalpies at the two pressures (100-to-0 psig -> ~13.3%). Drives flash-tank and vent-line sizing and the 'why is my return full of steam' diagnosis. A thermodynamic-ideal fraction; trap subcooling and line losses move the field value, and a flash-recovery vessel is sized from the manufacturer's data.
• Steam Main Size from Flow and Velocity - Sizes a steam main by mass flow against an allowable velocity: required area = (lb/hr x specific volume) / (velocity x 60), then the smallest Sch 40 nominal whose ID clears it and the actual velocity in that size. The volume a pound of steam occupies collapses as pressure rises, so the same flow needs very different pipe at 5 vs 100 psig. The velocity band (supply mains ~6,000-12,000 ft/min) is a recommendation, not a code limit; the engineer of record governs.
• Steam Trap Condensate Load and Required Capacity - The running condensate load (heat duty / latent heat) and the required trap capacity (load x a 2x-3x safety factor) at the operating differential - undersize it and the equipment floods on warm-up. The trap is selected from the manufacturer's capacity chart at the actual differential; warm-up, modulating, and stall conditions can demand a larger factor or a different trap type. Not the IMC 307 cooling-coil condensate drain.
• Steam Orifice / PRV Capacity (Napier) - Choked steam through an orifice or PRV by Napier's formula: flow chokes when P2 < 0.58 x P1, and the capacity W = 51.43 x Cd x A x P1 (saturated) then depends only on the upstream pressure. A liquid Cv (square-root in pressure drop) is wrong for choked steam, which is linear in P1; superheat needs a Ksh factor. A sizing aid, not a relief-valve certification.
• Pipe Pressure Rating and Required Wall (ASME B31.1) - The ASME B31.1 internal-pressure relation both directions: maximum allowable pressure from a wall thickness, or the minimum wall a design pressure demands - tying OD, wall, allowable stress S, weld-joint factor E, and the y-coefficient together (4 in Sch 40 A106-B -> ~1,637 psi). The allowable stress, joint factor, and y-coefficient are read from the applicable code edition's tables; a design screen, not a stamped calculation. The engineer of record and the AHJ govern.
• Filled Pipe Support Load per Hanger - The operating load each hanger carries: empty pipe + contained fluid + insulation weight per foot (from the cross-section and densities) times the hanger spacing (4 in Sch 40 water-filled at 14 ft -> 16.3 lb/ft, 228 lb/hanger). The MSS SP-58 operating support load that every hanger, rod, and attachment is then sized to. Bundled pipe weights are nominal mill values, water at 62.4 lb/ft^3; concentrated loads (valves, flanges) are added separately.
• Minimum Hanger Rod Diameter from Load (MSS SP-58) - The smallest carbon-steel threaded rod whose MSS SP-58 maximum safe load (at or below 650F) clears the per-hanger load after the temperature derate, with the utilization (228 lb -> 3/8 in at 37%). The single lookup that decides the rod stock on the truck. Above 650F apply the standard's derate; the engineer of record and the standard's current edition govern the final selection.
• Condensate Return Line Size From the Flash Steam - The return line size from the FLASH steam that re-boils off the condensate at the lower return pressure, not the liquid: flash = load x flash fraction, volumetric flow = flash x specific volume / 60, required area = flow / a return-velocity ceiling, then the smallest Sch 40 nominal that carries it (800 lb/hr at 13% flash to a 0 psig return -> 1-1/2 in). A return sized for the gallons of water floods and water-hammers; pair the flash fraction with flash-steam-pct. The lower velocity ceiling (~4,000 to 5,000 ft/min) and a wet, dry, or vacuum return each change the design; the engineer of record governs the return scheme.
• Branch Saddle Cutback Template (Pipe-on-Pipe) - The saddle contour ordinates for a branch pipe notched to sit on a run pipe for a welded branch connection: cutback(theta) = R - sqrt(R^2 - (r sin theta)^2) around the branch end, zero at the heel and toe (in line with the run) and maximum at the sides (2 in branch on a 6 in run -> 0.22 in max cutback). A larger run is a flatter surface, so the saddle is shallower. The geometric contour for a 90-degree same-centerline branch; the weld bevel, gap, and root face are added per the WPS, and a reducing or angled branch shifts the contour. A fit-up aid, not a weld procedure.
• Reducer Centerline Offset and Invert Continuity - The centerline offset = (large OD - small OD) / 2 and which surface stays continuous through a size change: a concentric reducer holds the centerline but drops the invert (a dam on a gravity drain, an air pocket on a pump suction); an eccentric flat-on-bottom holds the invert (correct on a sewer); flat-on-top holds the crown (correct on a pump suction). A 6 x 4 reducer offsets 1.0625 in. Standard lay lengths per ASME B16.9 (entered by the user); the lay length is a fitting dimension, not a code minimum.
• Flange Pressure-Temperature Rating (ASME B16.5) - The maximum allowable working pressure of a flange CLASS at a service temperature, read from the ASME B16.5 table with linear interpolation: a Class 150 carbon-steel flange is 285 psig cold but 200 psig at 400 F, and a Class 300 follows its own higher curve (635 psig at 400 F). Bundled ratings are Material Group 1.1 (carbon steel, e.g. A105); other material groups have their own tables. The value is the flange's rating; the weakest component (gasket, bolting, the mating pipe) can still govern the joint. The AHJ and the engineer of record govern.
• Branch Connection Reinforcement (Area Replacement, ASME B31.1) - Whether a branch opening cut into a pressurized run needs a reinforcing pad: the area-replacement check of ASME B31.1 para 104.3.1 (and B31.3 304.3 for process). The metal removed, A_required = t_rh x d1 x (2 - sin beta), is made up by the excess wall in the run (A1) and branch (A2) within the reinforcement zone; a shortfall is the pad area to add. An NPS 6 Sch 40 run with an NPS 2 Sch 40 branch at t_rh 0.10 is adequate on run excess alone (A1 0.37 >= A_req 0.21); raise the required wall and the same opening flips to needing a repad. The required walls come from the pressure design (pipe-pressure-rating); the engineer of record and the AHJ govern. The area balance, not a stamped branch-connection design.
• Expansion Joint / Loop Guide Spacing (EJMA 4D/14D) - Where the first two guides go so an expansion joint or loop compresses instead of buckling sideways: the first guide within four pipe diameters of the joint, the second within fourteen diameters of the first, per the Expansion Joint Manufacturers Association (EJMA) rule. A 4 in line (OD 4.5) guides at 18 in then 63 in past it (81 in from the joint); the distances scale directly with the diameter, the multipliers are the fixed rule. Beyond guide 2 the intermediate spacing comes from the EJMA table or the pipe-column stability calc. This places the planning guides; the anchor and joint selection govern.