Waterdrop TSU Review: Ultrafiltration Without the Drain Line (October 2026)
The Waterdrop TSU suits municipal cold-water kitchens that want ultrafiltration without a drain line. It needs a separate faucet and countertop hole, and it does not reduce TDS.
On this page (7 sections)
- The Waterdrop TSU at a glance
- What does the TSU filter, and what does it leave in the water?
- Does it really avoid a drain line?
- What installation details should you check first?
- How often do the TSU filters need changing?
- How does the TSU compare with other under-sink filters?
- Is the Waterdrop TSU a good fit for your sink?
The Waterdrop TSU is an under-sink ultrafiltration system for municipal cold water that does not need a drain line. It retains dissolved minerals and does not reduce TDS, and its separate faucet requires a hole in the countertop.
That makes it a fit for a kitchen where you want a dedicated filtered-water tap and can drill the counter. If you want a direct connection to your existing faucet or need TDS reduction, compare other system types before choosing.
The Waterdrop TSU at a glance
The TSU is a three-stage filter system with a 0.01 micron ultrafiltration membrane, a maximum flow rate of 1.05 GPM and a smart panel with four filter reminder lights. It uses mechanical water pressure, so it needs no power.
Waterdrop TSU: Best for a no-drain UF setup
- 0.01 micron ultrafiltration
- No wastewater or drain line
- Separate faucet included
- 6, 12 and 24 month filter schedule
A three-stage under-sink system for municipal cold water that retains minerals and does not reduce TDS. Plan for a separate faucet and countertop drilling.
Pros
- No wastewater or drain line
- No power needed
- Filter reminder panel
- UF filter life of 24 months
Cons
- Does not reduce TDS
- Separate faucet needs a drilled countertop hole
- Not suitable for well water or hot water
Its key distinction is the no-drain setup. Waterdrop says the system produces no wastewater, but it still needs a cold-water connection and its own faucet.
Who should choose the Waterdrop TSU?
Choose the TSU if your home uses municipal tap water, you want a separate filtered-water tap and you don't need lower TDS. The 24-month UF filter interval may also appeal if you want fewer membrane changes than the other two filter stages require.
Look elsewhere if you use well water, need hot-water filtration or want a system that lowers dissolved solids. The under-sink reverse osmosis buyer's guide explains what an RO setup offers and how it differs from ultrafiltration.
What does the TSU filter, and what does it leave in the water?
The TSU is designed to reduce substances such as chlorine, PFAS, taste, odor and heavy metals while retaining minerals. Ultrafiltration is not reverse osmosis, so it does not reduce TDS.
A TDS meter measures dissolved solids, including minerals such as calcium and magnesium. A similar reading before and after filtration does not tell you whether the filter has reduced the specific substances it is designed to address.
Waterdrop describes the membrane as 0.01 micron and says it helps filter the substances named above. Treat that as the system's stated filtration scope, not as a guarantee about every contaminant in your water.
If you need to know what is present in your tap water, consult your local water report or arrange appropriate testing. Then compare the filter's stated reduction claims with the substances you want to address.
Does it really avoid a drain line?
Yes. The TSU does not produce wastewater, which removes the drain connection used by reverse osmosis systems.
That can simplify the plumbing under a sink where adding a drain fitting would be difficult.
The trade-off is that this system does not reduce TDS. An RO system sends reject water to a drain as part of its process; read why reverse osmosis systems waste water to understand that difference.
The TSU also requires a dedicated faucet. Waterdrop says countertop drilling is required, so check whether your sink already has an unused faucet opening and whether the counter material can be drilled safely.
What installation details should you check first?
The TSU is intended for a standard under-sink cold-water connection and includes parts for 1/2 in and 3/8 in under-sink water pipes. Confirm your shutoff valve and available cabinet space before starting.
The system measures 14.81 in long, 4.68 in wide and 13.97 in high. Measure around the disposal, stored items and existing plumbing, and leave room to access the filter cartridges.
The separate faucet is the main planning step. If the counter has no spare opening, check the material and installation requirements before committing to a new hole.
For a general walkthrough of the process, see how to install an under-sink reverse osmosis system. The plumbing steps can differ by system, so follow the TSU instructions for its connections and faucet.
How often do the TSU filters need changing?
The TSU uses a staggered schedule: PP every 6 months, CT every 12 months and UF every 24 months. Its panel has four lights to remind you when filter changes are due.
The intervals make maintenance easier to plan, but actual service life can depend on water quality and use. Keep the replacement filter codes with your household records so you can order the correct cartridge when needed.
The under-sink water filter replacement guide covers the practical steps and timing questions that apply to cartridge changes. Follow the TSU instructions for its specific filter order and reset process.
How does the TSU compare with other under-sink filters?
The TSU stands out for its no-drain operation and separate faucet, while the alternatives make different trade-offs in connection style and maintenance. All four systems listed here retain minerals and do not reduce TDS.
The Waterdrop WD-TSA-UF connects directly to many compatible faucets and has a maximum flow rate of 1.5 GPM. Its filters have shorter stated intervals than the TSU's UF stage, and compatibility depends on the faucet's thread type.
The CuZn UC-200 uses an inline connection and does not require drilling for a separate faucet. CuZn gives it a service life of up to 5 years or 50,000 gallons, depending on incoming water quality.
The Waterdrop TSB includes a dedicated faucet and uses three filters with staggered replacement intervals. Its setup is closer to the TSU's, so compare the stated filter schedule and filtration features in the Waterdrop TSU vs TSA comparison.
Is the Waterdrop TSU a good fit for your sink?
The Waterdrop TSU makes sense when you want ultrafiltration without wastewater and can install a dedicated faucet. Its main limits are clear: it is for municipal cold water, does not reduce TDS and requires countertop drilling.
Pick the TSU if those conditions match your kitchen and you value a 24-month interval for the UF filter. Choose a direct-connect inline filter if you want to avoid a separate faucet, or compare RO systems if reducing TDS is part of your goal.
For a broader look at non-RO options, see our guide to the best under-sink water filters.
Frequently asked questions
Does the Waterdrop TSU reduce TDS?
No. The Waterdrop TSU uses ultrafiltration and retains dissolved minerals, so it does not reduce total dissolved solids.
A TDS meter reading may stay similar after filtration; use a reverse osmosis system if reducing TDS is your goal, and choose a filter based on the substances you want addressed.
Does the Waterdrop TSU need a drain line?
No. The TSU does not produce wastewater, so it needs no drain connection.
It does use a separate faucet, and installing that faucet requires a hole in the countertop; check the sink area and the countertop material before choosing this setup.
How often do Waterdrop TSU filters need replacement?
The TSU's PP filter is scheduled for replacement every 6 months, its CT filter every 12 months, and its UF filter every 24 months. Water quality and use can affect actual service life, so follow the system's reminder panel and its instructions for replacement.
Can you use the Waterdrop TSU with well water?
The TSU is designed for municipal tap water and is not suitable for well water. If your home uses a well, choose a system intended for that source or get the water assessed and confirm compatible pre-filtration with the manufacturer before connecting an under-sink filter.
