Retrofitting a snowmaking system for additive dosing is a supply-side job, not a gun job. You add a concentrate store, a make-down and day tank, a flow-paced metering pump, and one injection point on the main — then verify dose and performance. Existing guns, nozzles, and compressors are untouched.
That asymmetry is the whole commercial case for chemistry as an efficiency lever: the hardware you already own keeps working, and the retrofit lives in the pump house. This guide walks the actual scope of work — the regulatory gate first, then the equipment, the polymer-handling constraints that catch people out, and how to verify you are dosing what you think you are dosing.
Key takeaways
- Additive dosing is a supply-side retrofit: concentrate storage, make-down/day tank, flow-paced metering pump, injection quill, and mixing. No modification to snow guns or lances.
- The first step is regulatory, not mechanical — Austria and Bavaria prohibit all additives in snowmaking water by law, so no retrofit is lawful there regardless of engineering.
- Ultra-high-molecular-weight polymers are shear-sensitive and need hydration time; the make-down system, not the pump curve, is what usually determines whether performance shows up.
- Dose control is flow-proportional: pace the metering pump from the main's flow meter so ppm holds whether one gun or fifty are running.
- Retrofit freeze protection and materials compatibility for the concentrate loop; a dosing skid in an unheated space is the most common practical failure.
- Baseline your efficiency metrics before commissioning, or you will have no defensible way to show what the additive did.
What does an additive dosing retrofit actually involve?
Six elements: a bulk or tote concentrate store, a make-down system that hydrates the polymer correctly, a day tank of dosed-ready solution, a positive-displacement metering pump, an injection point on the water main, and instrumentation to pace and log the dose. Everything sits between the pump-house discharge and the distribution network.
| Element | What it does | Typical retrofit scope | |---|---|---| | Concentrate store | Holds product as delivered (tote, sack, or drum) | Bunded floor area in a heated space | | Make-down / hydration | Wets and hydrates polymer to a stable solution | Mixer + tank; low-shear transfer | | Day tank | Buffers hydrated solution for steady suction | Level switches, low-level dosing cut-out | | Metering pump | Delivers the dose at target ppm | Diaphragm/progressive-cavity, flow-paced | | Injection point | Introduces solution into the main | Quill into pipe centreline + static mixer or straight-run | | Instrumentation | Paces and proves the dose | Flow meter signal, stroke counter, dose log |
None of that is exotic — it is standard municipal and agricultural water-treatment practice. Anionic polyacrylamide has been metered into irrigation water for three decades under published application standards; the USDA NRCS anionic PAM practice specification sets out dilution, application-rate, and product-purity requirements (including the ≤0.05% residual free acrylamide ceiling) for exactly this class of chemistry. A snowmaking retrofit borrows that engineering wholesale; what changes is the target ppm and the temperature environment.
What has to be checked before any hardware is ordered?
The legal status of additives in your jurisdiction, and the terms of your own water abstraction and discharge permits. This gate is binary and it comes first: in some markets no dosing retrofit is permissible at any dose, and in others the constraint sits inside your permit conditions rather than in national law.
- National additive rules. Austria and Bavaria prohibit all additives in snowmaking water by law — SL6733 included. France discontinued additive use in 2005 through an industry-wide suspension of cryogenic additives by Domaines Skiables de France, not a statutory ban. Additives remain permitted in Italy, Switzerland, and non-Alpine geographies. The country-level picture is in snowmaking additive rules by country, and the frequently-mangled Snomax question in is Snomax banned in Europe.
- Water abstraction and discharge permits. Snowmaking water is usually abstracted under a permit whose conditions may speak to what can be added. The framework that governs this in the EU is the Water Framework Directive plus national implementations — see snowmaking additives and EU water law and snowmaking permits in Alpine areas.
- Product regulatory dossier. Ask the supplier for the substance-level position, not a marketing claim. For a polymer, that means the REACH Article 2(9) polymer exemption position and monomer registration status, plus the residual-monomer specification.
- Downstream water use. If your reservoir or catchment feeds anything with a drinking-water designation, the relevant benchmark is the EU Drinking Water Directive acrylamide limit of 0.1 µg/L, and your dose arithmetic should be documented against it.
Doing this in the wrong order is the expensive mistake. A dosing skid is cheap relative to a snowmaking capex programme; a permit dispute in December is not.
Where should the additive be injected?
Into the water main downstream of the main pumps and upstream of the branch distribution to the guns, at a single point, with enough turbulence or a static mixer to blend before the flow splits. One injection point serves every gun on that line, which is why per-gun hardware is unnecessary.
The practical constraints:
- After the high-shear equipment, not before. Ultra-high-molecular-weight polymer chains degrade mechanically under high shear, and chain length is what does the work. Injecting upstream of a multi-stage booster pump puts your active ingredient through the worst shear field in the system.
- Centreline injection. A quill that discharges into the middle of the flow blends far better than a wall tapping, which can leave a rope of concentrate hugging the pipe wall.
- Blend before the split. Either a static mixer or a defined straight run before the first branch. If the flow divides before blending, guns on different branches see different doses.
- Accessible and isolatable. Isolation valves and a bleed on the injection line, because you will need to service it mid-season.
How is the dose held at target ppm?
By pacing the metering pump from the main's flow meter rather than running it at a fixed stroke rate. Flow-proportional control keeps concentration constant as the number of running guns changes through the night, which is the difference between a documented dose and an average that means nothing.
Snowmaking flow is not steady. It ramps as guns come on, drops as the wet-bulb window closes, and swings with fan-gun versus lance mix. A fixed-output pump therefore over-doses at low flow and under-doses at peak — the two states in which you can least afford it. Pacing the pump from a 4–20 mA or pulse output on the existing flow meter fixes this, and gives you a dose log per shift as a by-product.
The arithmetic itself is simple, because 1 ppm is almost exactly 1 gram per cubic metre of water: at a 7 ppm target, 1,000 m³ of water takes 7 kg of active polymer. The full worked set of figures, including the concentrate-versus-active distinction that trips up pump sizing, is in how snowmaking additives are dosed in ppm. Size the pump for the active dose at maximum system flow, then check its turndown ratio covers minimum flow — turndown, not peak capacity, is the specification that usually gets missed.
What are the cold-climate and materials constraints?
A snowmaking pump house is a hostile place for a chemical feed system. The concentrate loop needs to stay above freezing, wetted materials need to be compatible with an anionic polymer solution, and hydrated polymer solutions are extremely slippery — a genuine slip hazard that belongs in the risk assessment.
- Freeze protection. Keep the concentrate store, make-down tank, day tank, and pump inside the heated envelope; heat-trace and insulate any line that leaves it, including the run to the injection quill.
- Hydration time. High-molecular-weight polymer needs to be properly wetted and given the supplier-specified hydration period before dosing. Skipping it produces fish-eyes and gel lumps, blocked strainers, and a dose that is nominally correct and functionally absent.
- Low-shear transfer. Use transfer methods the supplier approves for hydrated solution. Progressive-cavity or diaphragm pumps handle viscous polymer solution more gently than centrifugal transfer.
- Materials. Polyethylene, polypropylene, PVDF, and stainless wetted parts are the normal choices; confirm elastomer compatibility with the specific product.
- Housekeeping. Bunding, spill kit, and a wash-down plan. Polymer plus water on a concrete floor is slick enough to injure someone.
How do you prove the retrofit worked?
Baseline before you commission, then compare like conditions. Measure production in cubic metres of snow per megawatt-hour and per cubic metre of water, log wet-bulb alongside it, and compare treated and untreated runs at comparable wet-bulb rather than comparing season totals.
A defensible verification plan has four parts:
- Pre-retrofit baseline. At least one season, ideally two, of production, energy, water, and wet-bulb data at trail or line granularity.
- Dose verification. Stroke counts or mass-balance from tank level against water volume pumped, so you can show the ppm you actually delivered rather than the one you targeted.
- Paired-condition comparison. Treated and untreated lines, or treated and untreated nights inside the same wet-bulb band. Season-over-season comparison is confounded by weather and proves nothing.
- Water monitoring. Sampling against your permit conditions and the drinking-water benchmark, documented for the regulator before anyone asks.
The metric framework for the first two is set out in snowmaking efficiency metrics, and the supplier-side questions to ask before you get this far are in how to evaluate a snowmaking additive.
Where SL6733 fits
SL6733 is a two-component polymer additive — an ultra-high-molecular-weight anionic poly(acrylamide-co-sodium acrylate) for ice-recrystallization inhibition, plus a cold-water-swelling starch nucleant — specified at 6–7.6 ppm in snowmaking water. It is dosed exactly as described above: hydrated in the pump house, metered flow-proportionally into the main, distributed to whatever guns you already own. The product detail is in what is SL6733.
If you want the dosing scope mapped onto your own pump house — flow range, turndown, injection location, freeze protection, and a verification plan you can put in front of a regulator — request a pilot or send us a message. We price against the value the chemistry creates in your operation, not per kilogram.
SL6733 is pre-commercial, with EU lab pilots targeted for the 2026/27 season; dose rates are the specified operational range and any performance outcome is modelled until validated under pilot conditions. Engineering guidance here is general good practice, not a substitute for supplier specifications, a site-specific design, or legal advice on your permits.