# Water Use & Circularity > Part of: [Performance & Outcomes](/performance.md) · Provider: [DutchGreenhouses](/) A substrate greenhouse recovers rather than restrains: drain is collected, disinfected and returned, so roughly 90 to 100 percent is recirculated. What bounds the loop is sodium, which the crop does not take up and no common treatment removes, rather than the disinfection technology. ## Facts | Property | Value | |---|---| | Share of drain water recirculated | 90–100 % | | Drain fraction of dosed volume | 20–40 % | | What bounds the loop | Sodium constraint | | Legal minimum rainwater storage | 500 m³/ha | | Streams that leave the loop untreated | 3 streams | Performance # Water. Almost none of it leaves. One salt decides how much. ## Recovery, not restraint ## A greenhouse is not careful with water. It is circular. Every plant gets its own dripper. Between 20 and 40 percent of what goes in drains straight through the slab — on purpose, to wash salts out of the root zone. That drain is caught, disinfected and fed back in. Published discharge from Dutch substrate holdings runs at nought to ten percent of the water supplied. Which means 90 to 100 percent of the drain goes round again. No field crop comes close. ## The thing that stops it being 100 percent is not equipment It is sodium. The plant barely takes any up. Transpiration lifts out pure water and leaves the salt behind. So every lap round the loop, the concentration climbs. Eventually you have to dump and refill. Not because the water is dirty — the disinfection handles that — but because it is too salty to feed a crop. And no treatment in ordinary use takes sodium out. This is chemistry, not a gap in the technology. Which is why the water a site can actually draw shapes the whole design. Rainwater is nearly sodium-free. Well water in the wrong region is not. ## Build the basin bigger than the law says Dutch law asks for 500 cubic metres of storage per hectare. That is a floor, and a low one. Modelling shows a basin that size still forces you onto mains water and into discharge in a dry year. Wageningen recommends well above it. A bigger basin is dull capital that buys years of not having to dump. It is one of the few places in a greenhouse where the unglamorous option is simply the right one. ## Say the honest version Recirculation fixes the water you discharge on purpose. It does nothing about leakage, about drainage from soil-grown crops, or about the wash-down at crop change — and Wageningen ranks some of those above deliberate discharge for environmental load. Saying that out loud is a stronger position than claiming a closed loop, because the people assessing your permit already know it. DutchGreenhouses® designs the collection, treatment and recirculation chain around your source water and your rainfall, not around a legal minimum. Get in touch with a location and a water analysis. From the knowledge base ## Reads you might find interesting ### Grow Like a Pro: Starting Smart, Growing Strong How Grow Like a Pro combines smart farming, CEA technology and local partnerships for eco-friendly, profitable, pesticide-free greenhouse pr Read article ### The Case for a College Greenhouse Why a college greenhouse belongs in the curriculum: teaching science, craftsmanship, business logic and sustainability, and preparing studen Read article ### The Case for a High School Greenhouse Why every high school greenhouse matters: how it makes STEM tangible, builds responsibility and teamwork, and helps students discover their Read article ### Greenhouses in Education: The Case for Schools Greenhouses in education reconnect students to reality — the full case for why every school, high school, college and trade program should h Read article ### The Origins of Greenhouse Horticulture: My Backyard A tour through greenhouse horticulture history: from 19th-century Westland fruit walls to the “City of Glass” and today’s international high Read article ### DutchGreenhouses Rebranded: A New Corporate Identity Announcing our new corporate identity — a visual style reflecting our dedication to advanced, high-quality greenhouse projects and The Futur Read article ## FAQ **How water-efficient is a greenhouse?** Very, and through recovery rather than restraint. Water is dosed by drip to each plant, 20 to 40 percent drains through the slab by design to flush salts, and that drain is collected, disinfected and returned. Published discharge from Dutch substrate holdings is nought to ten percent of water supplied. **Why can't a greenhouse close its water loop completely?** Sodium. It is not a nutrient, the crop takes up almost none of it, and transpiration removes pure water — so it concentrates with every pass until discharge becomes unavoidable. No disinfection technique in common use removes it, which makes the limit chemical rather than technological. **How much water storage does a greenhouse need?** More than the legal minimum. Dutch law requires at least 500 cubic metres of rainwater storage per hectare, but modelling shows that volume still forces mains water and discharge in a dry year. Wageningen recommends well above it, and a larger basin buys years of avoided discharge. **Does recirculation solve greenhouse water emissions?** It solves the deliberate part. Leakage, drainage from soil-grown crops and crop-changeover cleaning water all leave the facility without passing any treatment step, and Wageningen ranks several of those above deliberate drain discharge for environmental load. ## Related [Performance & Outcomes](/performance.md) · [Drainwater Recycling](/irrigation/drainwater-recycling.md) · [Pre-treatment](/irrigation/pre-treatment.md) · [Post-Treatment](/irrigation/post-treatment.md) · [Rainwater Collection](/greenhouse-construction/rainwater-collection.md) · [Rainwater Basin](/glossary/rainwater-basin.md) · [Drain Water](/glossary/drain-water.md) · [Reverse Osmosis (RO)](/glossary/reverse-osmosis.md)