Watercalcs
Estimates only — verify before relying on results. Terms of Use
v1.0
New to this tool? Switch on the worked example (ACH from an IBC, dosed to a low-pressure flash mixer) to see how the tabs fit together. Your own entries are kept separately and come back when you switch it off.
Getting started

This tool helps you design a best-practice liquid chemical dosing system: from the drum, IBC or bulk tank through the pump to the injection point. Work left to right through the tabs; results and guidance update as you type.

  • Chemical & Dose - pick the chemical, enter the plant flow range and the dose range in whatever unit you normally use. The tool converts between product, active and metal bases and works out the pump flow range and turndown you need.
  • Storage & Suction - choose how the chemical is stored and where the pump sits relative to the liquid. This drives storage sizing, NPSH available, priming and syphon checks.
  • Pumps & Duty - select a pump type and duty arrangement; the tool checks capacity, pressure and turndown against what that pump type can honestly deliver.
  • Dosing Line - size the line, check velocity and pressure, and see whether you need a dampener, loading valve, carrier water or heat tracing.
  • Ancillaries & Safety - tick what your design includes; the tool compares it with best practice and shows compatible wetted materials.
  • Design Review - every issue found, ranked by severity, with a design summary. Report & Save exports it.

Tip: the gear icon in the header holds site conditions (ambient temperature, elevation, flow units) and the design targets the checks are measured against. The i icon explains the model basis and its limits. Lime and other slurries are out of scope.

Chemical

%
-
cP
kg/kg
°C

Plant flow and dose range

ML/d
ML/d
ML/d
Coagulants are conventionally quoted % w/v (mass of active per volume of product) and acids and bases % w/w. The tool applies the right conversion for the basis shown above; ppm v/v and mg/L as product are always available.

Dosing duty

Guide: using this tab

Describe where the chemical is stored and where the pump sits relative to the liquid. The tool sizes storage from the average duty, checks day-tank and bund practice, and calculates NPSH available at the pump suction from the liquid level, suction line losses, acceleration head and vapour pressure.

Enter liquid levels relative to the pump centreline: positive when the liquid is above the pump (flooded suction), negative when the pump lifts (IBC or drum with the pump on top, or a suction lance). Use the lowest operating level for NPSH - that is where priming and cavitation problems start.

Sanity-check: a diaphragm pump on top of an IBC with a lance to the bottom already has around 1 m of lift before pipe losses. Off-gassing chemicals such as sodium hypochlorite should never be lifted.

Storage arrangement

L
L
-
L
-
L
Fields that do not apply to the chosen storage type are ignored.

Pump suction

m
m
m
-
°C
Negative levels mean the pump is above the liquid (suction lift). Enter the bore of the suction tube or pipe, not the outside diameter.

Storage sizing

Suction conditions

Guide: using this tab

Choose a pump type and a duty arrangement. The tool works out the rated capacity each pump needs (with a stroke or speed margin from Settings), the turndown each pump must achieve, and compares both with the honest working envelope of that pump type - not just the catalogue extremes.

Turndown is the ratio of the largest to the smallest dose flow. Diaphragm pumps lose accuracy at short stroke lengths, so their reliable turndown is well below the nominal figure. Digital stepper-driven diaphragm pumps hold accuracy over very wide ranges but are limited to modest flows and pressures. Peristaltic pumps are gentle, self-priming and tolerate gas, but slip against high discharge pressures.

A single duty pump with no standby is a process risk on any dose that protects public health - the tool will say so.

Pump type

%
Sets the rated pump size. 70 to 85% leaves headroom.
m
spm
bar

Duty arrangement

-
-
% of duty
Only applies when a second pump cuts in on demand.

Pump selection check

Pump type comparison for this duty

Guide: using this tab

Size the discharge line and describe the injection point. The tool calculates peak and mean velocity, friction loss (laminar flow is common with viscous products), the discharge pressure the pump must develop, and whether a pulsation dampener, loading (back-pressure) valve, pressure relief valve, carrier water or heat tracing is needed.

Air locking is the classic dosing-line failure: gas collects at high points and the pump strokes against a compressible pocket. It is worst with off-gassing chemicals, suction lift, long lines and low velocities. The tool scores that risk and suggests the usual remedies.

Carrier water is optional. Enter a carrier flow to see the combined velocity, residence time and dilution at the injection point, plus the compatibility cautions for the chosen chemical.

Discharge line

m
-
m
bar g

Discharge-side devices

Tick what the design includes. Each row shows what best practice is for this design and why. These are the same items as the Ancillaries & Safety checklist - changing one changes the other.

bar

Carrier water

L/h
m
bar g

Line hydraulics

Line guidance

Guide: using this tab

Tick what your design includes. The tool compares each item with best practice for the chemical, duty and arrangement you have described, and lists anything missing in the Design Review. Modern dosing systems are cabinet-housed, bunded, instrumented for dose confirmation and laid out so that an operator is never exposed to a spray or squirt when changing a container or a pump head.

The materials section shows wetted-material compatibility for the selected chemical and a suggested set for pump heads, seals, valve balls and tubing. Always confirm against the supplier's safety data sheet and the pump manufacturer's compatibility data.

Dosing skid and instrumentation

Tick what the design includes. Discharge-line items also appear on the Dosing Line tab - the two lists are the same design.

Storage and handling safety

Tick what is in place. Rows are flagged against best practice for this chemical, quantity and location.

m
Other chemicals stored nearby

Tick everything stored in or next to this area, including chemicals for other dosing systems. The tool flags what is incompatible with the chemical dosed here, what is incompatible with each other, and what releases corrosive vapour into the room.

Guidance only. This tool does not assess hazardous substance storage, location compliance or certification requirements - engage a compliance certifier for those.

Chemical storage interactions

Wetted materials for this chemical

Guide: using this tab

Everything the tool has found, in one place. Critical items are process-risk or safety gaps that should not go to construction unresolved. Check items are worth a second look or a supplier confirmation. Notes are good practice reminders. The design summary table is what goes into the report.

Severity bands are prompts to look, not instructions to act: thresholds live in Settings and should be tuned to your site and the chemical supplier's data.

System schematic

Design snapshot

Issues and insights

Design summary

Guide: using this tab

PDF report opens your browser's print dialog with a formatted report of the sections you tick; choose "Save as PDF" as the destination. Browser headers and footers are switched off by the page. CSV gives the same sections as a flat table for a spreadsheet. Save design writes every input and setting to a JSON file in your downloads folder; Load design brings it back on any device.

Report

Sections to include

Save and load

The design file holds all inputs, settings and current results. Loading replaces what is on screen.

Autosave keeps your work in this browser between visits.