How to use this
The lessons follow the water from the street to the steriliser: basics → softener → RO → ultrapure / pharmaceutical water → clean steam, then the building's boilers, cooling towers and closed loops, then Legionella, which touches all of them. Each lesson has a What, a Why and a How. Use the Calculators and the Clean steam simulator alongside.
Softener sizing
How long a softener runs between regenerations, and the salt it uses.
Capacity per ft³ of standard 8% cross-linked cation resin, roughly: 20,000 grains at 6 lb salt, 25,000 at 10 lb, 30,000 at 15 lb. Lower salt doses are more salt-efficient but give less capacity.
Reverse osmosis performance
Recovery, rejection, and what the membranes are really doing.
The temperature correction uses a typical polyamide membrane curve (flow changes about 3% per °C). Normalising to 77 °F / 25 °C is how operators compare today with last month fairly.
RO pressure check
Enter today's gauges to see the pressure drops and net driving pressure.
Osmotic pressure ≈ 1 psi per 100 ppm TDS; the concentrate side uses the concentrated TDS. Typical limits shown are for brackish polyamide elements; your system's design sheet rules.
Pool water balance (LSI)
The Langelier Saturation Index: the same scale-or-corrode index used for cooling towers, RO concentrate and boilers.
LSI near 0 (−0.3 to +0.3) is balanced; positive tends to scale (cloudy water, crust on tile and heater), negative tends to corrode (etched plaster, metal parts, heater). Alkalinity is corrected for cyanuric acid, as pool industry practice does.
Pool chlorine dose
How much liquid chlorine (sodium hypochlorite) to raise free chlorine.
Rule of thumb: 1 gallon of 12.5% raises 10,000 gallons by about 12.5 ppm. Pour slowly in front of a return with the pump running; never mix with acid.
Building water pressure
Pressure at the top fixture, and whether you need boosters or a PRV.
0.433 psi per foot of height. An RPZ alone typically costs 10–15 psi at flow. Many codes cap static pressure at fixtures around 80 psi.
Which backflow device?
Answer three questions; local code and the water authority have the final say.
Backflow test check
Enter a tester's readings to see pass/fail against typical criteria.
Pipe disinfection
Volume of a new or repaired line, and the chlorine to reach a disinfection dose.
Follow the code and procedure in force (AWWA C651/C652, plumbing code); neutralise heavily chlorinated water before it goes to drain where required.
Carbon tank EBCT (dialysis)
Empty bed contact time: how long water spends in the carbon. Dialysis needs ≥ 10 minutes in total.
Dialysis pre-shift chlorine
Total chlorine, tested before each patient shift.
Dialysis water demand
How much product water the RO must deliver.
Culture and endotoxin results
Compare a dialysis water result with typical ISO 23500 maximum and action levels.
Conductivity ⇄ resistivity
Two ways of saying the same thing. Resistivity is used for very pure water.
Theoretically pure water at 25 °C: 0.055 µS/cm = 18.2 MΩ·cm. Readings are temperature-compensated to 25 °C, except the USP <645> Stage 1 test, which uses the uncompensated value against a temperature table.
Legionella temperature zones
Drag to see what Legionella does at each water temperature.
Blue: below about 77 °F, dormant · amber to orange: the growth range, about 77–122 °F, deepest around the 95–108 °F peak · red: above about 122 °F, no growth and killed faster the hotter it gets (but a scald risk).
Cooling tower water balance
Evaporation, blowdown and makeup from the tower's load and cycles.
Rule of thumb: evaporation ≈ recirculation × range × 0.001 (1% per 10 °F). Drift taken as 0.002% of recirculation.
Boiler blowdown
How much water you must blow down to hold the boiler's dissolved-solids limit.
Feedwater TDS here is the blend of condensate (nearly pure) and softened makeup. More condensate return → lower feed TDS → more cycles → less blowdown.
Glycol freeze protection
Approximate freeze points for inhibited glycol solutions (by volume).
Typical published values; check your glycol supplier's chart. Burst protection (slush but no cracking) reaches much lower than the freeze point.
Closed-loop inhibitor top-up
How much product to add to bring a loop back into its control range.
Follow the vendor's dosing instructions and add through the pot feeder; retest after it has circulated.
Softener regeneration, step by step
Press Next to walk through a co-current regeneration on a typical control valve.
Clean steam generator (unfired, plant-steam heated)
Plant steam heats a tube bundle inside the evaporator. Purified water boils on the shell side, passes a separator, and leaves as clean steam. Two control loops keep it steady: pressure (by throttling the plant steam valve) and level (by the feed pump). Change the demand and watch them work; then try the interlock buttons.
Simplified teaching model, not a real unit's tuning. Real generators add: feedwater preheat/degassing from blowdown or condensate heat, continuous blowdown, sample cooler with on-line conductivity, safety valves on both sides, and vacuum breakers and traps on the plant-steam side.
What you're watching
- Pressure loop: a PID controller compares the clean-steam pressure with the setpoint and opens or closes the plant-steam valve. More heat into the bundle → more boiling → more pressure. Raise the demand and the pressure dips, then the valve opens to recover it.
- Level loop: boiling takes water away; the feed pump replaces it to hold the level over the bundle. Too low exposes hot tubes (overheating, scaling, superheat); too high risks carrying water droplets into the steam (wet steam, carry-over of endotoxin and impurities).
- Interlocks: low-low level, high-high pressure and bad feedwater close the plant-steam valve no matter what the PID wants, and the trip latches: heating stays off until the cause is cleared and an operator presses Reset trip, so a fault can't quietly come and go. That's the same "safety beats control" rule as in the PLC trainer.
Quiz
Pick an answer to see why. Your best score is remembered on this computer.