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Calcimator

Shower Valve Calculator

Size shower valves based on showerhead count, body sprays, flow rates, and water pressure. Determines thermostatic vs pressure-balance needs.

Inputs

Results

Total flow demand (GPM)

2

Valve port size (in.)

0.5

Thermostatic valve needed?0
Volume controls needed0
Supply pipe size (in.)0.5
Pressure at head (PSI)39
Pressure adequate?1
Valve cost estimate$80.00
Trim kit cost$150.00
Total valve + trim cost$230.00
How to Use This Calculator
  1. Enter the number of showerheads (fixed, rain, and handheld combined).
  2. Enter the number of body spray jets if your shower system includes them.
  3. Set the flow rate per showerhead in GPM — WaterSense-certified heads are 2.0 GPM or less.
  4. Enter your static water pressure in PSI (measure at the nearest hose bib).
  5. Check Thermostatic Valve Needed — if the result is 1, a thermostatic valve is recommended for your multi-outlet system.
  6. Use the Total Valve + Trim Cost to budget for the shower valve system before installation.

How the result changes with Flow per showerhead (GPM)

Flow per showerhead (GPM)Total flow demand (GPM)Valve port size (in.)
1.151.20.5
1.521.50.5
1.9820.5
2.352.40.5

What each input means

Number of showerheads
Fixed, handheld, and rain showerheads.
Body spray jets
Wall-mounted body spray outlets.
Flow per showerhead (GPM)
Gallons per minute per showerhead. WaterSense max is 2.0 GPM.
Flow per body spray (GPM)
Gallons per minute per body spray jet.
Water pressure (PSI)
Static water pressure at the shower supply (check at nearest hose bib).

What each result means

Total flow demand (GPM)
Combined flow from all outlets running simultaneously.
Valve port size (in.)
Minimum valve inlet/outlet port diameter.
Thermostatic valve needed?
1 = thermostatic recommended, 0 = pressure-balance OK.
Volume controls needed
Separate volume control valves for multi-outlet setup.
Supply pipe size (in.)
Minimum supply pipe diameter to feed the valve.
Pressure at head (PSI)
Estimated pressure after valve drop, elevation, and friction.
Pressure adequate?
1 = sufficient (20+ PSI), 0 = may need booster pump.
Valve cost estimate
Rough-in valve body + volume controls.
Trim kit cost
Handles, escutcheon, showerhead trim.
Total valve + trim cost
Complete shower valve system cost (labor not included).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Number of showerheads = 1, Body spray jets = 0, Flow per showerhead (GPM) = 2, Flow per body spray (GPM) = 1 = 5 input(s) provided
  2. Calculate Total flow demand
    Total flow demand = showerheadFlow + bodySprayFlow
    2 = 2
  3. Calculate Valve port size
    0.5 = 0.5
  4. Calculate Thermostatic valve needed?
    Thermostatic valve needed?
    0 = 0
  5. Calculate Volume controls needed
    Volume controls needed
    0 = 0

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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