The “50 Shades Of Gray Water Reuse” project was a 2015 maker prototype that routed bathroom-sink water toward a toilet tank using a PVC reservoir, pump, solenoid valve and Arduino controller. It illustrates one possible reuse concept—not a validated product, proven water-savings system or approved plumbing design. Whether a similar installation is allowed depends on its water source, treatment, end use and local rules.
What the “50 Shades” project was
In a May 30, 2015 feature, Hackaday described TVMiller’s Arduino-powered attempt to reuse bathroom sink water for toilet flushing. The reported arrangement used a zig-zag of PVC pipe beneath the sink as a reservoir, a 12 V solenoid, a water pump rated at 240 L/h, and an Arduino with an LCD to track water saved. Hackaday said the pump activated after a toilet flush. Those are components and behavior reported in the feature; they do not establish tested performance or a measured volume of water saved. Hackaday’s 2015 project account does not provide a complete bill of materials, engineering drawings, water-quality measurements, code review or maintenance schedule.
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What graywater means—and why definitions vary
Graywater is generally used household water from wash-related activities, distinguished from wastewater that has contacted human waste. The boundary is not universal. TeachEngineering’s educational explanation includes water from showers, sinks, baths, dishwashers and clothes washers, while plumbing provisions can define permitted source streams differently. For example, the 2021 International Plumbing Code (IPC) lists bathtubs, showers, lavatories, clothes washers and laundry trays as onsite graywater sources, and prohibits diversion of wastewater containing urine or fecal matter. TeachEngineering’s classroom explanation is useful background, not a substitute for a jurisdiction’s plumbing rules.
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Can sink water be reused to flush a toilet?
It can be a potential non-potable use in a properly designed and approved system, but the 2021 IPC model-code provisions do not treat untreated sink water in a homemade reservoir as automatically suitable for toilet flushing. Under that code edition, graywater used to flush water closets or urinals must receive disinfection and treatment through a compliant onsite reuse system. It also says untreated onsite graywater should not remain in a collection reservoir for more than 24 hours. These are model-code provisions, not a statement that the 2021 IPC has been adopted in every location or that its text alone determines what a specific homeowner may install. Read the 2021 IPC nonpotable-water provisions alongside the locally adopted edition and amendments.
#1 Best Overall
- WATER-SAVING DUAL FLUSH TOILET REPAIR KIT: Easily converts a standard toilet into a dual flush toilet that saves water by reducing the amount of water used with each flush. The permafit silicone seal is also chlorine and chemical resistant and will not warp.
- ELIMINATES TOILET LEAKS: Eliminates common leaky toilet problems due to a worn-out flapper, handle or faulty flapper chain.
- HASSLE-FREE INSTALLATION: Drop-in installation without tools in 5 to 10 minutes - tank removal not required. This has an adjustable height of 11-13.8 inches.
- TOILET FLUSH VALVE COMPATIBILITY: The Dual Flush Converter works with standard 2 in. flush valves and requires a 10-inch minimum clearance from highest point of the flush valve opening to the inside of the tank lid. NOT COMPATIBLE WITH MANSFIELD TOILETS. The HYR451T combines two products that together will increase your toilet's efficiency: HYR271 Dual Flush Converter and HC630 HydroClean fill valve.
- DUAL-FLUSH LIGHT-TOUCH LEVER UNIQUE SPLIT HANDLE DESIGN: The short center lever is the Quick Flush setting that uses significantly lower water volumes for liquids and paper – this setting is needed 4 out of 5 times. The second complete push lever at end is the Full Flush that uses the normal amount of water for solids.
How this prototype differs from other reuse approaches
A sink-to-toilet setup is only one possible arrangement. Laundry-to-landscape systems, other landscape irrigation uses, and professionally treated onsite reuse systems have different source water, end uses and design requirements. A comparison should start with these practical distinctions rather than assume that all graywater is interchangeable:
- Source stream: Laundry, bath or shower, lavatory and kitchen water may be treated differently by local rules. Do not infer that a source allowed for one use is allowed for another.
- End use: Subsurface irrigation, other landscape uses and toilet flushing present different exposure and treatment considerations. The 2021 IPC requirement for treated and disinfected water specifically applies to flushing water closets and urinals under that model code.
- Storage and treatment: The 2021 IPC limits untreated onsite graywater retention in a collection reservoir to 24 hours and requires treatment and disinfection for toilet flushing. Requirements depend on the applicable local code.
- Plumbing and upkeep: A system needs a design that accounts for source and destination plumbing, treatment components, maintenance access and the authority’s approval process. The Hackaday feature does not document these items sufficiently to serve as construction plans.
The available sources do not establish comparable costs, performance or payback for these approaches, so the prototype cannot be ranked against other systems on savings or value.
Rank #2
- WATER-SAVING DUAL FLUSH TOILET REPAIR KIT: Converts a standard toilet into a dual flush toilet that saves water by reducing the amount of water used with each flush. The HYR451T combines two products that together will increase your toilet’s efficiency: HYR271 Dual Flush Converter and HC630 HydroClean fill valve
- COMPATIBILITY: The Dual Flush Converter works with standard 2 in. flush valves and requires a 10-inch minimum clearance from highest point of the flush valve opening to the inside of the tank lid. NOT COMPATIBLE WITH MANSFIELD TOILETS.
- FLUSH VALVE REPLACEMENT INSTALLATION TIP: Be sure to place the Dual Flush Converter directly in the center of your existing flush valve
- IMPORTANT INSTALLATION TIP: Do not remove overflow tube and flush valve from toilet tank; the Dual Flush Converter is a replacement to the existing flapper; slide the blue silicone dome gasket down the overflow tube, seating the gasket into the flush valve
- ELIMINATES TOILET LEAKS: Eliminates common leaky toilet problems due to a worn-out flapper, handle or faulty flapper chain; the permafit silicone seal is also chlorine and chemical resistant and will not warp
What to check before planning household graywater reuse
- Identify the source and intended use. Tell your plumbing authority which household water you want to collect and whether it would go to irrigation or toilet flushing. Rules may permit some source-and-use combinations but not others.
- Check the locally applicable plumbing requirements. Ask the authority having jurisdiction which code edition and amendments apply, whether a permit or approved system is required, and what treatment, storage, cross-connection protection and inspection rules govern your intended use.
- Check public-health requirements. The EPA’s California summary describes treated onsite graywater use under California provisions and notes that minimum water-quality requirements are determined by the local public-health authority. It is a California example, not a nationwide approval. Consult the EPA’s California onsite reuse summary and confirm requirements with the relevant local agency.
- Use local guidance for design and installation. Do not treat a maker-project feature as plans or proof of compliance. Have the system reviewed through the required local permitting and public-health process before connecting it to household plumbing.
What about saving laundry water for a garden?
Laundry-to-landscape reuse is a different use case from routing lavatory water to a toilet, and it still raises questions about local approval, handling and the products used in the wash. In a 2016 Grist advice column, Greywater Action founder Laura Allen advised using graywater promptly to limit stagnant storage: “It’s best to use gray water as soon as possible so it doesn’t go anaerobic and breed bacteria,” she said via email. That dated advice does not replace current local rules; check local requirements and guidance on suitable water sources and landscape application. Grist’s laundry-water advice column discusses the garden-use question.
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Rank #4
- WATER-SAVING TOILET FLUSH VALVE: The HydroRight replacement toilet flush valve easily converts most standard toilets into a dual-flush water-saving toilet which uses up to 70% less water for liquids and paper.
- REPAIRS COMMON LEAKY TOILET ISSUES: Eliminates the most common problems in toilets that cause leaks as this flush valve replaces a worn-out toilet flapper, chain and handle which can often break.
- LEVER STYLE HANDLE: Includes lever style split handle flush activator that gives you a choice to use the quick-flush setting which uses less water volume for liquids and paper or the full-flush setting which uses the normal full flush water volume to accommodate solids.
- COMPATIBILITY: Fits 1.6 to 3.5+ GPF (gallons per flush) standard 2-piece toilets with 2 in. flush valve and requires 10-inch minimum clearance from highest point of the flush valve opening to the inside of the tank lid; Note: Will NOT FIT Mansfield toilets and is not compatible
- EASY NO-TOOLS REQUIRED INSTALLATION: Simple Drop-in installation without tools in less than 20 minutes with NO TANK REMOVAL required.
Rank #3
- Universal Compatibility: This 3-inch toilet internal replacement kit is designed as a direct replacement for many major-brand 2-piece toilets, including Glacier Bay N2316, Glacier Bay N2428R-DF / N2428R-DF-17, and AquaSource T801, as well as other standard 2-piece toilet tanks with a 3-inch drain opening
- Measure Your Toilet Tank’s Flush Valve: Before you purchase this dual flush toilet kit, please verify that your toilet's dimensions match those of our toilet repair kit
- Easy and Quick Installation: Our toilet flusher replacement kit includes an installation wrench for faster, correct installation. Get it done like a pro without searching for compatible tools
- Dual-Flush Water-Saving Design: Features dual flush push buttons: a full flush for solid waste and a half flush for liquid waste. Maximize the water-saving benefits of dual flush valve replacement parts
- Dedicated Support: If you have any questions about installation or compatibility, our support team is ready to help. Contact us and we'll make sure you get the help you need
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