For small polyphosphate refill orders, freight and fixed handling charges—not the crystal price—set your cost floor. The practical answer is to stop pricing refills per kilogram of material and start pricing them per landed refill unit: calculate the true delivered cost of your smallest realistic shipment, allocate every fixed fee across it, then build the refill price upward from that number. A 25 kg polyphosphate crystal order can easily land at several times its ex-works material value once air freight, clearance, and last-mile costs are included.

This guide is written for importers, distributors, filter and cartridge assemblers, and water-treatment service companies that resell polyphosphate refills in small quantities. It gives you a repeatable cost model, a worked example, and the levers that actually reduce landed cost per refill.

Why small polyphosphate refill orders behave differently from bulk media

Bulk water-treatment media is priced like a commodity: the material cost dominates, and freight is a relatively small percentage. Small refill orders invert that relationship. Several cost elements are fixed per shipment regardless of size:

• Customs brokerage and entry filing
• Last-mile delivery, which is often priced per stop rather than per kilogram
• Export packing, labelling, and documentation
• Bank and payment charges on an international transfer
• Receiving, inspection, and put-away at your warehouse

When these fixed elements are spread across 20–30 kg instead of 500–1,000 kg, the per-kilogram landed cost rises sharply. Any pricing model that starts from the supplier’s unit price and simply adds a percentage markup will understate your real cost on small orders and quietly erode margin on every refill you sell.

A terminology note before you model anything

Siliphos is a trade name associated with slow-dissolving polyphosphate glass products; it is not a generic chemical name, and formulations, dissolution behaviour, and available certifications vary between suppliers and products. Do not treat all polyphosphate crystals, phosphate media, or “siliphos-type” materials as interchangeable when you compare quotes.

Functionally, these materials are used to inhibit new calcium carbonate scale deposition and, depending on formulation, to help form a protective film relevant to corrosion control. They do not soften water in the ion-exchange sense, do not remove hardness ions, do not remove existing scale deposits, and are not a filtration or disinfection step. Dissolution rate, recommended dosage, contact time, and temperature and pH limits must come from the specific product’s technical data sheet, not from a generic assumption.

Build the landed cost, then price the refill

The model has two stages. First, compute landed cost per kilogram for a realistic shipment. Second, convert that into a refill price that covers repackaging and your target margin.

Stage 1: land the shipment

1. Define the refill unit. Determine how much crystal goes into one cartridge, housing, or refill pouch your customers actually buy. This is the unit you will price, not the kilogram.
2. Get the material price at a named Incoterm. Ex-works, FOB, and CIF quotes are not comparable. Record the Incoterm and the currency.
3. Determine chargeable weight. Freight is billed on the greater of actual weight and volumetric (dimensional) weight. Polyphosphate crystal in a carton can be dense, but pack sizing still changes the billed weight.
4. Add insurance as a small percentage of goods plus freight, if you insure.
5. Add duty and taxes based on the HS code applied by your destination customs authority. Duty is often calculated on a CIF-type value, so freight increases duty as well as freight cost.
6. Add fixed fees: brokerage, entry filing, terminal or documentation charges, and last-mile delivery.
7. Add receiving and internal handling at your own facility.

Stage 2: convert landed cost into a refill price

Add the costs that only appear when you break bulk: refill pouches or cartridges, labels, weighing and filling labour, sealing, and any batch labelling your customers require. Then apply margin using one consistent convention and state it in your price list:

• Margin on selling price: price = total refill cost ÷ (1 − target margin %)
• Markup on cost: price = total refill cost × (1 + target markup %)

These two produce very different numbers at the same percentage, which is a common source of disagreement between sales and finance teams.

Illustrative model: 25 kg versus 100 kg

The figures below are hypothetical and are included only to show how the arithmetic works. Replace every number with your own quotes.

Three things stand out. First, freight alone exceeds the material value on the small air shipment. Second, duty is charged on freight too, so expensive shipping raises duty. Third, moving from 25 kg to 100 kg cuts landed cost per kilogram by more than half even though the material price never changed.

From landed cost to a shelf price

Assume a 1 kg refill pouch, repackaging cost of 1.50 per unit, and a target margin of 35% on selling price. On the consolidated 25 kg shipment, the delivered cost per refill is about 11.58, giving a price of roughly 17.82. On the 100 kg LCL shipment, delivered cost is about 7.31 and the price falls to roughly 11.25. Same product, same margin rate, very different customer-facing price.

Levers that lower landed cost per refill

• Increase quantity per shipment, not per order line. Buying 100 kg twice a year usually beats buying 25 kg four times if storage and shelf life allow.
• Change the packaging, not the chemistry. A larger bulk pack inside one carton reduces pack count and can reduce dimensional weight and handling.
• Consolidate with other products. Sharing a shipment with other non-conflicting items dilutes brokerage, entry, and last-mile charges.
• Match the transport mode to the reorder cycle. Slower consolidated freight lowers freight cost but lengthens lead time and increases the working capital tied up in stock, plus the risk of running out between shipments.
• Repack locally instead of importing finished refills. Importing bulk crystal and filling pouches or cartridges in your own market often reduces freight weight and duty exposure compared with importing pre-packed retail units.
• Audit the fixed fees. Brokerage, terminal handling, and last-mile charges vary significantly between providers and are the easiest line items to renegotiate.

What to confirm with a supplier before you finish the model

• Product identity: exact material description, polyphosphate type, and particle size range.
• Performance basis: dissolution behaviour and recommended dosage under stated temperature, pH, and flow conditions.
• Application limits: maximum water temperature, contact time requirements, and any incompatibilities.
• Regulatory status for your market: whether the exact product is permitted for the intended use, including potable water. A “food grade” description alone does not establish drinking-water suitability for a specific product, application, and destination.
• Documentation: technical data sheet, safety data sheet, certificate of analysis, and country of origin.
• Logistics data: pack dimensions, net and gross weight per carton, cartons per pallet, HS code, and available Incoterms.
• Commercial terms: validity period of the quote, currency, and whether the price is fixed or indexed.

Requesting pack dimensions and gross weight early matters more than most buyers expect, because those two numbers determine your chargeable freight weight and therefore your entire landed cost calculation.

Frequently asked questions

Does a larger order always reduce landed cost per kilogram?

Usually, but not automatically. Larger orders reduce the fixed-fee share and often unlock better freight rates, yet they also increase inventory carrying cost, storage space, and the risk of holding stock that ages or becomes obsolete. The correct order size is the one that minimises total cost of ownership, not the one with the lowest freight per kilogram.

Can I price refills with a simple percentage markup on the supplier’s unit price?

Only if your landed cost is close to the supplier’s unit price, which is rarely true for small orders. Applying a markup to the ex-works price on a 25 kg air shipment can leave you selling below your own delivered cost.

Is polyphosphate crystal a water softener?

No. It does not remove calcium or magnesium from water. It is used to inhibit new scale formation and, depending on formulation, to support corrosion control. It also does not remove existing scale, filter particulates, or disinfect.

Should freight be allocated by weight or by value?

For refill pricing, allocate by weight or by unit, because freight is driven by weight and volume. Allocating by value distorts the price of low-cost, heavy items and hides the true cost of the refill.

How often should the model be recalculated?

Re-run it whenever freight rates, fuel surcharges, duty rates, or your supplier’s Incoterm changes, and at least once per annual price review. Freight volatility is usually the largest single swing factor in small-order refill economics.

Planning a polyphosphate refill programme?

If you are working through this model for a specific refill product, share a few details and ENVO CHEMICAL can respond with relevant technical and commercial information: the application (scale inhibition, corrosion control, or both), source-water hardness, pH and temperature, the housing or cartridge type and refill quantity you plan to offer, the pack size you prefer, your quantity per shipment, destination country and port, and the specification or documentation you need. With those details, the landed-cost calculation and product selection can be handled together rather than as two separate exercises.