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Plant Engineering Calculator

Updated Sep 18, 2026

Boiler Conductivity & Blowdown Calculator — Cycles, Flow, Heat & Water Cost

Set a continuous boiler blowdown rate from feedwater and boiler-water conductivity, then quantify cycles of concentration, feedwater demand, heat carried above makeup temperature and annual treated-water value.

Live calculationWorking shownPrivate in browser

Inputs

Results

Cycles of concentration 10.00
Required continuous blowdown 1111 kg/h
Blowdown / feedwater 10.00 %
Feedwater required 11111 kg/h
Blowdown heat above makeup 196.3 kW
Annual blowdown 6667 m³/year
Annual water + treatment value $8000
More actions

Shared links reopen these inputs. Recent and saved calculations stay in this browser unless you clear site data.

Formula

cycles=conductivity boiler/conductivity feed; B=S/(cycles−1); feed=S+B; heat=B(hblowdown−hmakeup)/3600.

Your calculation, step by step

These steps use the values currently entered above so the result can be checked independently.

  1. 1.Cycles = boiler conductivity ÷ feedwater conductivity = 2000.00 ÷ 200.00 = 10.0000.
  2. 2.Continuous blowdown B = steam S ÷ (cycles − 1) = 10000.00 ÷ (10.0000 − 1) = 1111.111 kg/h.
  3. 3.Feedwater F = S + B = 10000.00 + 1111.111 = 11111.111 kg/h; B/F = 10.000%.
  4. 4.Heat above makeup = 1111.111 × (720.00 − 84.00) ÷ 3600 = 196.2963 kW.
  5. 5.Annual blowdown ≈ 1111.111 × 6000 ÷ 1000 = 6666.67 m³; entered water/treatment value = $8000.00.

How to use this calculator

  1. Enter measured or design values using the units shown beside each field.
  2. Review the live results and the substituted calculation steps before using the estimate.
  3. Check the assumptions below, then continue to a related calculator when the next engineering decision needs another model.

Worked example

Feedwater conductivity of 200 µS/cm and a 2,000 µS/cm boiler setpoint gives 10 cycles. At 10,000 kg/h steam, ideal continuous blowdown is about 1,111 kg/h; the calculator also annualizes hot-water and treatment losses.

Assumptions and limits

  • Compare conductivity on the same temperature-compensated basis, commonly 25°C.
  • Conductivity is a practical dissolved-solids concentration proxy, not a universal fixed TDS conversion; calibrate against site chemistry.
  • Assumes dissolved solids leave mainly with blowdown and steam carryover is negligible.
  • Use the boiler OEM and water-treatment specialist limits for the actual conductivity setpoint.

How to interpret the result

Treat the primary result as an engineering screening value, then use the secondary outputs to understand scale, energy or operating impact. Confirm site measurements, equipment limits and applicable standards before making a design or control change.

Questions engineers ask

How do conductivity readings become cycles of concentration?

The calculator uses the ratio of boiler-water to feedwater conductivity as a practical concentration proxy when both measurements are on the same compensated basis. It does not assume conductivity equals TDS by one universal conversion factor.

Why is continuous blowdown B = S/(cycles − 1)?

With negligible dissolved solids leaving in steam, feedwater solids enter with F = S + B and leave mainly with blowdown. The steady-state solids balance gives cycles = F/B, so B = S/(cycles − 1) and blowdown is 1/cycles of feedwater.

Can this calculator choose the boiler conductivity setpoint?

No. The setpoint must come from boiler OEM limits and the water-treatment program. This owner quantifies the water/heat consequence of an entered setpoint; it does not prescribe chemistry.

Continue the calculation

Use the next calculator in the same engineering workflow instead of restarting from search.

boiler blowdownboiler blowdown heat recoveryboiler makeup water
Methodology. MAXScanner shows the governing formula, entered values and calculation outputs so the estimate is auditable. The calculator is a screening aid; assumptions and equipment-specific limits remain part of the engineering review.