Domestic filtration, water softeners and pumps

Domestic pump calculator: establish the household duty

For a new pressure-pump selection, start with the flow required by the house and the head the pump must provide. Record the supply level, outlet elevation, pipe route, required outlet pressure and losses through pipework and treatment equipment. Daily water use and the peak flow required at one time are different inputs.

Use DOM-005 Pump Duty (Fixture Count) when building a duty from household fixtures, then DOM-003 Domestic Pump Selector to compare models. For an existing pump, use DOM-002 Pump Match and check the original curve and operating duty. The Grundfos-to-DAB sample report shows why a returned candidate can still be a poor curve match.

A pump's maximum flow and maximum head are not a single operating point. Check the selected duty on the current manufacturer's curve, together with the controls and installation limits. For field irrigation, use the separate irrigation pump sizing guide.

Grundfos-to-DAB pump curve comparison

View the worked sample and downloadable PDF for the inputs, calculation result, manufacturer references and limitations.

Domestic water filtration and whole-house filter sizing

Tenselo's DOM-001 Domestic Filtration calculator helps water professionals assess a whole-house, under-sink or single-tap filtration arrangement. Choose the application, enter the peak flow, and select the sediment, carbon and UV stages to be assessed. Results describe the selected stages and their sizing requirements.

Whole-house or single-tap treatment?

A whole-house filter serves the incoming supply, while a point-of-use filter serves a particular tap. Use the flow required at that treatment point. Simultaneous household demand can be different from the flow through a kitchen filter, so the two applications should not share an assumed design duty.

Rainwater tank and bore-water filtration

Use the bore-water filtration and treatment guide to connect the laboratory results, design flow and intended use to a preliminary treatment pathway.

Start with the source, intended use, available pressure and water-test results. The domestic sizing tool does not replace a water-quality assessment. For rainwater or bore water, use water-test interpretation to review the supplied results and missing information before choosing the treatment stages.

Where the assessment identifies a need for iron removal, the reverse osmosis calculator or the ultrafiltration system sizing calculator, continue with the relevant treatment workflow. Confirm equipment performance, maintenance needs and the final arrangement with a specialist.

For an off-grid bore or surface-water duty, use the solar water pump calculator. It connects daily water demand and total dynamic head to pump flow, winter solar energy, PV array size and water-storage capacity.

Domestic water softener sizing

DOM-004 Domestic Water Softeners assesses resin capacity, vessel size, service flow, salt per regeneration and the interval between regenerations. Enter water hardness, daily demand and the flow conditions. A house supply with short peak demands differs from a steady tank-fill duty; check the appropriate operating case.

See a worked domestic water-softener example where the peak household flow, rather than the hardness load, controls the resin charge and vessel size.

For larger process duties, see industrial water softener sizing. For the water supply itself, the domestic calculator catalogue also includes pump selection, pump replacement and rainwater tank yield and sizing.

Tenselo provides software calculations rather than a laboratory testing or filter-installation service. Public examples are static; project calculations require authorised application access. See plans and availability. A calculated filtration arrangement is not drinking-water certification.

Domestic water-softener sizing: a worked software example

This hypothetical example was run in Tenselo's DOM-004 Domestic Water Softeners calculator on 15 September 2026. It sizes a whole-house unit from the daily hardness load and the service-flow requirement. It does not use a customer's water analysis or select a supplier model.

Inputs

• Daily softened-water demand: 1,000 L/day
• Total hardness: 250 mg/L as CaCO3
• Iron: 0 mg/L for this example
• Target run used for the hardness calculation: 5 days
• Salt dose: 150 g NaCl per litre of resin
• House flow: 30 L/min average and 45 L/min peak

Calculated result

The water contributes a hardness load of 250 g CaCO3 per day, or 1,250 g across the five-day design run. At the selected salt dose, the calculator uses an operating capacity of 55 g CaCO3 per litre of resin.

The hardness load alone would require about 23 L of resin. DOM-004 increases the charge to 68 L because the smaller bed could not pass the 45 L/min household peak within the calculator's resin-flow check. The returned vessel is a generic 1465 composite FRP vessel, 14 inches by 65 inches, with an estimated 82 L resin capacity at the stated freeboard.

What to check before equipment selection

The 30 L/min average flow exceeds the returned bed's continuous rating. DOM-004 treats short household draw-offs as an intermittent duty and directs long tank fills or irrigation loads to its separate tank-filling mode. Check that the water supply can deliver the backwash flow, review iron and other fouling risks, and confirm the resin, valve and vessel against current supplier data.

This public example summarises the verified calculator output. Live calculations and the complete report require authorised Tenselo application access. Interpret the water test first when the incoming water quality is uncertain.