4 Best Dual Tank Water Softeners (Twin Tank) [November 2023]

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Never wait for a regeneration cycle again.

If you’re looking for the best twin tank water softener in 2023, we’re here to help.

After scouring the market, reading customer reviews, and corresponding with manufacturers, we’ve compiled this list of the best twin tank water softeners, based on performance, resin quality, efficiency, and customer satisfaction.

🥇 Best Twin Tank Water Softeners

📊 Comparison Chart of Dual Tank Water Softener

SystemFleck 9100SXT Dual Tank Water Softener
Fleck 9100SXT Dual Tank Water Softener
DROP Duplex Smart Water Softener
DROP Duplex Smart Water Softener
US Water Systems Synergy Plus Water Softener
US Water Systems Synergy Plus Water Softener
Crystal Quest Commercial Water Softener System
Crystal Quest Commercial Water Softener System
Flow Rate20 GPMNot indicated7 – 25 GPM15 – 25 GPM
Grain Capacity24K –110K32K, 48K, or 64K18.75K, 25K, 37K, 50K, or 63KUp to 90K
Regen MethodMeteredMeteredMeteredMetered
Warranty10 years5 years10 years on tanks
7 years on valves & control head
1 year

⭐ Reviews – Dual Tank Water Softener 2023

We love this on-demand water softener because it offers the best value for its performance features, helping you to save up to 40% of salt and water with its efficient performance. There are 15 grain sizes to choose from, from moderately-sized 24,000 and 32,000-grain softeners for residential use, all the way up to 120,000-grain twin-tank units for heavy commercial use.

Key Features:

  • Choose between 15 grain sizes – No other dual tank water softeners in this guide have as many size options as the Fleck 9100SXT. These are 14 size upgrades beyond the smallest 24,000-grain model.
  • Efficient regeneration – As a twin-tank softener, this Fleck model already produces soft water more efficiently, with less water and salt waste, than single-tank water softeners. It has a few additional efficiency features, too, including fully adjustable control, enabling it to provide a tailored performance that suits your situation.
  • Great system warranty – The Fleck softener’s valves have a 5-year warranty, while the tanks have a reassuring warranty of 10 years. Your purchase is protected under the warranty’s terms.
Fleck 9100SXT ConfigurationsPrice

Best For:

Anyone looking to invest in the best-value twin-tank water softener, or anyone who’s specifically looking for a two-tank softener offering as many efficiency features as possible.


  • Efficiency is a standout benefit of this Fleck water softener. You have full control over adjusting the 3- or 5-cycle control for the soft water regeneration process, allowing you to tailor the system to maximize its efficiency and reliability.
  • We think it’s super useful to have so many different water softener sizes to choose from. You can choose the exact size for your situation, which means you don’t have to jump up to a higher size than you need, but if you do need the biggest unit for commercial purposes, you have plenty of options.
  • You also have flexibility when choosing your bypass, from 3/4″ and 1″. There’s the option to purchase a Quick Pro connect kit at an extra cost, to simplify installation.
  • Once you do the initial programming for the 9100SXT softener, you won’t ever have to touch the control head again. In the event of a power outage, the system has an internal capacitor that will keep the time set for up to 48 hours. Its non-volatile memory standard also means that its pre-set functions will never be forgotten.


  • Nothing so far!

This professional-grade system uses smart technology and progressive flow to safely and efficiently soften your water. It can be connected to the DROP Hub and paired with the DROP leak detectors to provide water softening and leak protection in one. Choose between three system capacities, from 32,000 grains to 64,000 grains.

Key Features:

  • 3 grain sizes available – The DROP Duplex Smart Water Softener comes in three grain sizes: 32,000 grains (ideal for most families), 48,000 grains (for larger homes), and 64,000 grains (for commercial use).
  • Smart system with app connection – Like all DROP water treatment systems, the Duplex Smart Water Softener uses smart functioning to conserve water based on your varying water demands. It has a few exclusive benefits, including compatibility with the DROP leak detectors and connectivity with the DROP app, so you can monitor your water usage and adjust settings remotely.
  • 5-year warranty – The 5-year warranty covers the entire system and isn’t quite as reassuring as the 10-year tank warranty for our top pick Fleck system.
DROP Duplex ConfigurationsPrice (Standard)Price (w/ DROP Hub)

Best For:

Folks who want to invest in a premium twin-tank water softener that they can use as part of a smart ecosystem of leak detectors and water treatment systems.


  • The smart aspect of the DROP Duplex Smart Water Softener is its obvious selling point. We love the convenience of being able to connect the system to the DROP Hub and download the DROP app to monitor the system’s performance and water usage remotely.
  • There are a few unique design features of this softener that enable it to operate efficiently, including progressive flow, which allows for a continuous supply of soft water based on your water usage, with minimal water and salt waste.
  • We think DROP has addressed the very real risk of plumbing leaks as effectively as possible. You can buy DROP smart leak detectors and connect them to the DROP Hub alongside your water softener, giving you peace of mind (not to mention a way to quickly shut off your water supply if a leak is detected, regardless of your location).


  • This premium twin-tank water softener comes at a premium price. You might be unable (or unwilling) to spend at least $3,500 upfront on the smallest model.
  • DROP products only work with the DROP Hub. That’ll add another $200 onto your initial investment.

This system is about 20% cheaper than comparable dual tank water softeners, while still offering all the features of a pricier model, including high-efficiency softening, app connectivity, and a durable 10% crosslink resin.

Key Features:

  • 5 system sizes available – Choose between 5 sizes for the US Water Systems Synergy Plus Water Softener, ranging from 18,750 grains (with a peak flow rate of 7 GPM) to 63,000 grains (with a peak flow of 17 GPM).
  • Durable design – There are a few durable design features of this softener, including the long-lasting 10% crosslink resin, the lack of moving parts (there are just two in the water stream) to reduce the risk of breakdowns and repairs, and the use of brine for regeneration, which keeps the resin cleaner and reduces fouling.
  • Long warranty on tanks and valves – This US Water Systems softener has one of the best warranties we’ve seen. The tanks have a lifetime warranty, while the valve and electronics have a 10-year warranty (most competitors have a 5-year warranty for these components).
USWS Synergy ConfigurationsPrice (Standard)Price (w/ 5 Micron Magna)
7 GPM$1,430.51$1,599.66
10 GPM$1,542.71$1,721.21
15 GPM$1,715.26$1,892.91
20 GPM$1,955.81$2,133.46
25 GPM$2,121.56$2,286.46

Best For:

Anyone with a smaller budget who wants to spend less than $2,000 on a twin-tank water softener without compromising on performance quality or durability.


  • We think affordability is an obvious benefit of the US Water Systems Synergy Plus softener, especially if you’re looking for a smaller model. There’s no point in spending more money than necessary on a system that might be too big for your home if the smallest and most affordable US Water Systems model, the 7 GPM 18,750-grain softener, is more than adequate for you.
  • It’s good to see a 10% crosslink resin in this system, especially given its low upfront cost. 10% crosslink resin lasts almost twice as long as the standard 8% crosslink resin that’s included by default in most water softeners. That means less maintenance and less money spent on replacing the resin over the system’s lifespan.
  • US Water Systems is another manufacturer that understands the convenience of app connectivity. You can pair the US Water Systems Synergy Plus with the free Waterlogix companion app, giving you remote access to a dashboard where you can monitor the system and adjust settings.


  • The largest model is 63,000 grains, so you don’t get the same breadth of choice for sizing as you do with Fleck. If you need a softener for heavy commercial use, the US Water Systems Synergy Plus models might not cut it.

This water softener system has a higher starting price than our top two picks on this list, but it also has a higher starting flow rate of 15 GPM, ensuring no interruptions to your water flow. Plus, it’s another high-efficiency option, despite being a single-tank unit, and reduces water consumption with its timer control valves and fully adjustable backwash cycles.

Key Features:

  • 8 flow rates to choose from – The Crystal Quest Commercial Water Softener is available in 8 flow rates, from 15 GPM (ideal for most homes) all the way to 205 GPM (for heavy commercial use).
  • Efficient, high-flow performance – This single-tank softener has a larger tank and higher flow rates than other softeners with single tanks, and even some dual-tank systems. It has several features to support performance efficiency, including a flow controller that limits backwash flow, and a self-adjusting backwash controller that minimizes maintenance.
  • 1-year warranty – All customers receive a 1-year warranty for this softener.
Crystal Quest ConfigurationsPrice
15 GPM$2,990
20 GPM$3,200
35 GPM$4,200
60 GPM$5,195
75 GPM$7,595
185 GPM$12,695
200 GPM$14,695
205 GPM$16,695

Best For:

Folks who want the efficiency benefits of a twin-tank water softener without necessarily investing in a system with two tanks.


  • This Crystal Quest system used to be a twin tank system, but has now been updated to a larger single tank configuration. Nonetheless, the product is intended to offer efficient performance, wasting less water and salt in the process.
  • Quality and durability are obvious from the look and feel of this system. Its composite fiberglass tanks are durable and heavy-duty, designed to provide years of efficient performance.
  • The unit has a self-adjusting backwash controller that allows for maintenance-free operation. No need to mess with the softener settings until you get the soft water regeneration process just right – the system is smart enough to do it for you.


  • The 1-year warranty isn’t as good as the other system warranties on this list.
  • Customer feedback is very limited so far

🧾 Twin Tank Water Softener Buyer’s Guide

Ready to buy a twin tank water softener for your home? Keep reading for all the information that’s worth knowing before you make a purchase.

🤔 What is a Dual Tank Whole House Water Softener?

A dual tank water softener, otherwise known as a twin-tank water softener, is a water treatment system that tackles hard water issues at your home’s point of entry.

A twin-tank softener is an upgraded version of a single-tank conventional softener. While a conventional softener has just one resin tank, a twin-tank softener has two independently operating resin tanks. When one tank reaches capacity, the other tank can be used immediately while the first tank is regenerating.

👨‍🔧 Read more about the best single tank water softeners in this post.

❔ How Does a Twin Tank Water Softener Work?

To understand how a twin tank water softener works, we need to understand the performance of a conventional water softener with a single resin tank.

Water softeners regenerate – a process that washes away the accumulated hardness minerals and replenishes the resin beads with sodium ions – every two to three days. During this 2-3-hour period, a conventional single tank system is temporarily unable to provide soft water to a home. Usually, regeneration is set to perform overnight, when a household is less likely to need access to soft water.

Twin-tank water softeners run continuously, providing consistent access to soft water. These water softeners work exactly the same as single-tank water softeners, except they use two resin tanks instead of one.

twin tank water softeners

A twin-tank unit operates using one resin tank at a time. Once the sodium in one tank is depleted, the tank regenerates, and the second tank – which contains a replenished resin – can be used instantly.

💭 Do I Need a Dual Tank Water Softener?

Most people don’t need a twin-tank water softener, but you may prefer to use a softening system that gives you constant access to soft water.

In some situations, a twin-tank water softener may be a necessity. For instance, if you live or work in a shared residence, or you live with family members who work overnight, you might need access to soft water around the clock.

You may also need a dual tank water softener if you run water-based appliances overnight, and you want to prevent hard water damage from occurring during the system’s brief downtime during regeneration.

✔️ Benefits of Twin Tank Water Softeners

Here are some of the biggest benefits of dual-tank water softeners:

  • Constant soft water access – We love this benefit. The two resin tanks allow for constant soft water production, so you can avoid hard water in your home 24/7.
  • More efficient performance – Twin-tank water softeners typically waste less salt and water during operation. This is because, rather than regenerating to a schedule (which often means that the system regenerates when there is still salt remaining in the resin tank), it only regenerates when it needs to.
  • 24-hour pipe/appliance protection – Because dual tank water softeners offer constant access to soft water, your pipes and appliances will be protected from hard water around the clock. If you want to avoid using hard water in your home altogether, twin tank water softeners offer the solution for you.

📋 Considerations When Purchasing a Twin Tank Water Softener

When searching for a twin tank water softening system, consider the following things:

Your Water Consumption

Start by working out your average daily water consumption.

The amount of water you use should determine the size of your water softener. If you use more water than the average household, your water softener will need to regenerate more frequently. Undersizing a system will mean it regenerates too often, wasting more water than necessary.

faucet water flowing

It’s important to properly size your water softener based on your water consumption to minimize the frequency of regenerations.

However, it’s important not to purchase a dual-tank system that’s too large for your water consumption, either, which may lead to underregeneration – increasing the likelihood of bacteria growth in the tanks.

👨‍🔧 Learn how to choose the right-sized water softener in this guide: What Size Water Softener Do I Need?

Flow Rate

Flow rate is another important factor to consider when shopping for the best dual tank water softener system.

Flow rate is measured in gallons per minute, or GPM. The higher a water softener’s flow rate, the greater the volume of water a softener can provide per minute. If the flow rate is too low, the system may be unable to provide enough water to meet your demands. If the flow rate is too high, your pipes and appliances could end up sustaining damage.

Most dual tank systems have a water flow of 7-25 GPM. For the average family of 4, we recommend a flow rate of between 12 and 20 GPM.

Capacity You Need

Water softeners are sold in numerous different capacities, from 24,000 grains to 120,000 grains. Choose the right twin-tank water softener capacity for your situation.

Capacity refers to the amount of resin in the softener tanks. The larger the system capacity, the more equipped it is to deal with high volumes of water for extended periods of time.

Capacity also relates to your water hardness. The harder your water, the more sodium ions will be required for the ion exchange process. A larger-capacity system is helpful for homes with particularly hard water because the larger resin bed can hold more sodium at once, extending the operating time between each regeneration cycle.

Don’t know your water hardness? Buy an at-home hardness test to measure the hard water minerals in your water supply. You’ll get a reading in GPG, or grains per gallon:

  • 3.5-7 GPG is moderately hard
  • 7-10 GPG is hard
  • Anything over 10 GPG is very hard

For most families of 2-6, a twin-tank water softener that’s between 24,000 and 32,000 grains per gallon is more than adequate. But if you live in a big home or use a lot of water, upgrade to a suitable system capacity for your needs.

Your budget

Make sure your budget is large enough to cover the initial and ongoing costs of a twin tank water softener.

Because of their more efficient performance and the material costs of the additional tank, dual tank softeners are more expensive up-front than single-tank systems.

However, the higher upfront cost gives way to lower ongoing costs. A dual-tank system can help you save money on water and salt in the long run because the water regeneration process only occurs when the resin beads are completely depleted.

Calculating budget

The average starting price of a twin-tank water softener is $1,400 – about 10-20% more expensive than a comparably sized single-tank unit.

You may also need to make room in your budget for the cost of a professional installation, which is about $200.


You’ll need to be prepared for the maintenance responsibilities of owning a twin-tank water softener.

Like single-tank systems, dual tank systems are salt-based, the brine tank should be replenished with salt whenever it runs low.

Check your brine tank at least once a month and make sure it’s one-third full of salt, minimum. If not, add more salt to the tank, making sure not to overfill.

Aside from adding salt to the tank, additional periodic maintenance might be required, such as replacing worn parts and cleaning the unit. Check your user manual for more details.

Ongoing Costs

The biggest ongoing cost of owning a twin-tank water softener is salt. An ion exchange water softener can’t treat hard water without salt.

The average whole-house water softener uses up to eight 25-kilogram bags of salt every year. Luckily, salt is pretty affordable, and you can get some good deals online, especially if you buy in bulk.

Water softeners also waste a small amount of water during their soft water regeneration cycles, which will add to your monthly water bill.

Remember, dual tank water softeners are more efficient and waste less water/salt than single-tank systems because they only regenerate when necessary, so your ongoing costs for water and salt should be lower than if you owned a single-tank unit.


When a water softener has been certified by an independent third party, it means it has been rigorously tested and deemed safe and effective for its purpose.

NSF Certification for water softeners

There are several important certifications that a twin-tank water softener may have:


NSF/ANSI 44 applies to residential water softener systems that use a cation exchange resin and use either sodium chloride (salt) or potassium chloride during regeneration.

If a water softener has achieved an NSF 44 certification, it means it has been proven to reduce water hardness below 1 grain per gallon, and meets requirements for structural integrity and material safety.


NSF/ANSI 372 is a certification that water softener manufacturers can apply for to prove that their product has a completely lead-free design.

A twin-tank water softener with an NSF 372 certification has been tested for material safety and won’t add lead into your water.

NSF certifications aren’t essential, but they offer peace of mind and proof of quality, safety, and performance.

🧐 How to Install a Twin Tank Water Softener

The process of installing a twin-tank water softener is similar to installing a single-tank water softener. The main difference is that you have two brine tanks to install, rather than one.

Check your user manual for tailored instructions on how to install your water softener. Below, we’ve outlined the general step-by-step process:

  1. Gather your equipment. The softener should come with a valve, a meter and meter cable, numerous fittings, a drain line, a bypass, pre-filled resin tanks, a brine tank, and tank connections. You may need to buy additional pipes, screws, adaptors, and other small items needed for the job.
  2. Choose the install location. Ideally, the water softener should be placed as close as possible to your main water line’s point of entry into your home, before your water heater. There should be a firm, level base to place the tanks and enough room around the installation spot for maintenance.
where to install twin tank water softener
  1. Plumb in the system. Shut off your water supply and follow the instructions in your manual to plumb in your water softener. Make sure to adhere to your local plumbing codes.
  2. Install the resin tanks. Both tanks should be pre-installed with resin, but if not, add the resin yourself. Attach the control head/ control valve on top of one tank.
  3. Connect the drain line. Your water softener can drain to a floor drain, a washing machine drain, a utility sink, or a sump pit.
  4. Flush the system. Follow the instructions in your manual to flush water through your softener and remove trapped air from the system.
  5. Fill the brine tank. Add salt to below the “max fill” line in the brine tank.
  6. Plug in the control valve. Plug the valve into a nearby power outlet, then insert the meter cable into the meter.
twin tank installation

More of a visual learner? Take a look at videos online, like this one (for the Fleck 9100 SXT). Again, they won’t give you specific instructions for your water softener, but they’ll be helpful in helping you to determine whether installing this type of water softener is something you could handle yourself.

🧠 Frequently Asked Questions

Are twin tank water softeners better than single-tank softeners?

Performance-wise, twin-tank softeners are better than single-tank water softeners for anyone who needs a steady flow of soft water at all times, or anyone who wants to greatly reduce salt and water waste during system regenerations. But for most families, a single tank softening system that regenerates overnight, while you’re asleep, is more than adequate.

Why does my water softener have 2 tanks?

A conventional water softener has 2 tanks because one tank (the resin or mineral tank) houses the resin, while the other tank (the brine or salt tank) houses the softener salt. Some softeners, called twin-tank water softeners, have two resin tanks and a salt tank – so three tanks in total. Having two resin tanks allows the softener to provide constant access to soft water and minimizes salt and water waste.

Is a dual tank water softener worth it?

A dual tank water softener is worth it if you have a specific reason to need access to soft water 24/7 or you want to reduce salt and water waste as much as possible, saving money in the long run. But twin-tank softeners don’t perform significantly better than single tank systems, so you may prefer to spend less upfront on one of these systems.

Can you put two water softeners together?

Yes, in theory, you could put two water softeners together, but there wouldn’t be much point in doing so. There’s no need to double soften your water because a single water softener will completely remove hardness minerals if the settings are correct. The better alternative, if you’re looking for a solution that will give you soft water at any time of the day, is to buy a two-tank water softener.

  • Laura Shallcross
    Senior Editor

    Laura is a passionate residential water treatment journalist who holds an undergraduate degree in Print Journalism and a master’s degree in Creative Writing. Over a span of 5 years she's written on a range of topics including water softening, well water treatment, and purification processes.

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