Hard water at 25 grains per gallon or higher will scale a showerhead, a kettle and a tankless water heater in a matter of months. A dual tank water softener is the fix most homeowners land on, because two resin tanks rotate through regeneration so the house never runs on hard water while one of them recharges. We went through the top dual tank systems on the market for 2026 and compared them on grain capacity, control valve, flow rate, iron handling and the warranty terms that decide how long they last.
The short version: if your hardness is severe or your household uses a lot of water at once, a twin tank setup is worth the extra footprint and the higher purchase cost. If you are on a mild municipal supply in a small home, a single tank may serve you fine. We explain how to tell the difference further down, along with the sizing math and the installation mistakes that show up over and over on home improvement forums.
Every system in our list uses a metered, demand-initiated control valve, which means the unit regenerates based on gallons used rather than on a clock. That single design choice typically cuts water and salt consumption noticeably compared with older timer-based valves, and it is the reason we would not look at a timer valve in 2026 unless the budget is extremely tight.
If you are still deciding between a general whole-house unit and a dedicated two-tank system, our general water softener guide covers the basics first. If your supply comes from a well, start with our well water softener picks because iron and sediment change the sizing entirely.
Top 3 Best Dual Tank Water Softeners for Hard Water (October 2026)
These three stood out from the field. The first is the one we would put in a house with above-average demand, the second pairs strong feedback with mid-range capacity, and the third is the lowest-cost route into a two-tank system.
DuraWater Fleck 9100 SXT 48,000 Grain…
- Twin tank soft water 24/7
- 1.5 cu ft resin per tank
- Metered on-demand valve saves about 15 percent
DuraWater Fleck 9100 SXT 64,000 Grain…
- 64000 grain capacity
- Digital 9100 SXT valve
- Six capacity options
North Star NST45ED1 45,300 Grain Two Tank
- 45300 grain capacity
- NSF certified
- City or well water ready
Best Dual Tank Water Softeners for Hard Water in 2026
Here is the full lineup at a glance. All seven are metered two-tank systems, and the differences come down to capacity per tank, valve size and how each one handles iron.
| Product | Specifications | Action |
|---|---|---|
| DuraWater Fleck 9100 SXT 48,000 Grain Twin Tank |
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 DuraWater Fleck 9100 SXT 64,000 Grains Per Tank |
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| DuraWater Fleck 9100 SXT 64,000 Grain Dual Tank |
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| North Star NST45ED1 45,300 Grain Two Tank |
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 AFWFilters 64k Iron Pro Dual Tank with Fleck 9100SXT |
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 AFWFilters 32,000 Grain Dual Tank with Fleck 9100SXT |
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 AFWFilters 48k Iron Pro Dual Tank 1 Inch Valve |
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1. DuraWater Fleck 9100 SXT Twin Tank 48,000 Grains – Best Overall
DuraWater Fleck 9100 SXT Twin Tank Water Softener, 48,000 Grains, Black
48000 grains total
1.5 cu ft resin per tank
10 x 54 in mineral tanks
14 x 36 in brine tank
Pros
- Resin ships fully loaded in both tanks
- Twin tank keeps soft water flowing during regeneration
- Metered valve cuts water and salt use
- Highest review base in the group
Cons
- Drain line and fittings are not included
- Needs plumbing skill or a plumber to install
This is the system we kept coming back to. The Fleck 9100 SXT is the workhorse control valve in the residential trade, and pairing two of them in a rotating cabinet gives you 48,000 grains of usable capacity with about 1.5 cubic feet of resin loaded in each 10 by 54 inch mineral tank. Buyers consistently describe the setup as straightforward once the plumbing is in place.
The detail that stands out above the valve is how the system ships. The resin arrives already loaded in both tanks, which means you are not hauling 100 pounds of loose media from a bag into each tank in a wet mechanical room. That alone cuts a couple of hours and a lot of mess off an installation.
Reviewers report roughly 15 percent less water and salt consumption than a timed regeneration valve of the same capacity. In practice that means fewer refills of the brine tank and less discharge going to the drain, which matters more than most people expect once you look at a yearly water bill.
The real feedback base is what sets this one apart. With 50 reviews and a 4.6 average, it is the only unit in our lineup with enough owner history to say anything about durability over multiple years, and the reports skew consistently positive on setup ease and on the value compared with what a local plumbing company charges for a single tank.
The limitation to plan around is straightforward: no drain line, no fittings, and no instructions for the plumbing side. That is normal for this category, but it means you are either comfortable with household plumbing or you are paying a plumber for the connection work.
What you get for the money
The package is complete for a working softener: the 9100 SXT metered valve, two 10 by 54 inch mineral tanks, a 14 by 36 inch brine tank with a safety float, and a 1 inch plastic bypass. Everything you need to soften water is in the box.
What is not in the box is the connective plumbing. You will supply a drain line, fittings, and whatever pipe supports your layout. Ask your plumber about 1 inch versus 3/4 inch line here, because the bypass supplied is already 1 inch and downsizing it is an unnecessary step.
Who should skip it
If your home is small and your hardness reading is low, the 48,000 grain capacity here is more than you need and the two-tank format wastes floor space you may not have. Check your measured grains per gallon first before committing.
If you are on well water with more than about 8 ppm of iron, this model is a hardness-only design. You would want an iron-rated configuration like the AFW Filters units further down instead.
2. DuraWater Fleck 9100 SXT 64,000 Grains Per Tank – Best for Very Hard Water
USA Fleck 9100 SXT Twin Tank Metered On-Demand 64,000 Grains Per Tank Water Ships Partially Loaded with Resin
64000 grains per tank
128000 grains total
2 cubic feet capacity
24 x 12 x 57 in
Pros
- Largest total capacity of any unit in the group
- Upgraded paddle wheel meter adds metering durability
- Includes bypass with threaded yoke and hardness test kit
Cons
- Tanks ship partially loaded with resin
- Lowest average rating in the group
- Heaviest configuration here
When hardness runs past 40 grains per gallon, capacity becomes the whole game, and this is the biggest system in the group at 128,000 grains across two 64,000 grain tanks. A homeowner dealing with extreme hardness quoted in the forums picked a 160,000 grain configuration of this type and reported four months of solid operation, which is the scale of problem this unit is designed for.
The paddle wheel meter is a genuine upgrade over the standard meter in the base 9100 SXT. The meter is the part that counts gallons to decide when to regenerate, and it is also a common failure point, so the rugged version is worth noting if you are installing this at a house with high daily use.
Two things work against it. First, the tanks ship partially loaded, so you are buying resin separately and budgeting time to fill them. Second, the 3.7 average is the lowest of the seven, and the rating spread is unusually wide, with a meaningful share of one-star reviews. That pattern usually points at setup friction rather than a defective valve.
We would only pair a system this large with a genuinely large home or a demanding application. Over-sizing a softener in a small household is not a free upgrade, because the metered valve will still regenerate on demand but the salt and footprint cost is real.
Check your floor space before ordering
At 24 by 12 by 57 inches overall, this is the most physically demanding unit we looked at. Two full-size mineral tanks plus a brine tank need a mechanical room corner, not a closet.
Measure the drain route too. A two-tank system needs a drain line capable of handling the discharge flow during regeneration, and a long run to an unsuitable drain is the classic reason an install gets quoted higher than expected.
Where the ratings split
Owners who filled the resin themselves and got the programming right tend to rate it highly, and the 64,000 per tank figure means fewer regenerations per day at high hardness. The lower ratings cluster around partial resin loading and the extra setup step it creates.
If you are comfortable with a weekend of work and comfortable sourcing resin separately, the capacity is worth it. If you want a turnkey install, a fully loaded system will save you the most trouble.
3. DuraWater Fleck 9100 SXT 64,000 Grain Dual Tank – Best Value
Fleck 9100 SXT Metered Dual Tank Softener 24/7 Soft Water (64,000 Grain)
Digital 9100 SXT metered valve
64000 grain capacity
Black mineral and brine tanks
1 in noryl bypass
Pros
- 4.6 average with no low-star reviews
- Toll-free customer support from the seller
- Multiple capacity options to match household size
Cons
- Very small review base for a whole house system
- Valve programming needs care on first setup
This listing carries the same 9100 SXT valve as our top pick at a larger 64,000 grain capacity, and it is the configuration we would choose for a family of four or five on hard municipal water. The build is a complete system: digital metered valve, black mineral and brine tanks, and a free 1 inch noryl plastic bypass included in the box.
What separates it from the sibling models is the seller support. Toll-free customer support from the seller is not something every listing in this category offers, and on a system where first-time programming is genuinely fiddly, having someone to call removes a real source of frustration.
The honest weakness is the sample size. Twelve reviews is thin for a whole-house appliance, so we are relying on the fact that the valve itself is a proven, widely used design rather than on this listing’s own track record. Buyers report that setup is easy once the valve is programmed and that hardness reduction is effective.
Not a single one- to three-star review appears in the feedback. Sixty-six percent of owners gave five stars and the rest gave four, which is an unusually clean distribution for a component this large.
Choosing between the capacity options
This system is available in grain capacities from 24,000 through 80,000, so you can match tank size to household demand instead of buying more resin than you need. Pick the smallest capacity that covers your measured daily grain load with a reserve margin.
If you have a tankless water heater, note that continuous soft water matters most here, because the heater has no tank to buffer hard water and manufacturers often require treatment to keep the warranty valid.
Who should look elsewhere
Skip this if you are on a well with significant iron. This is a hardness-focused configuration with no iron pretreatment, and iron will gradually blind the resin bed.
Also skip it if you need a documented long service history. Twelve reviews cannot tell you what a valve looks like after five years, and buying a used unit is worse, since resin that has sat in water for a year is a gamble no spec sheet covers.
4. North Star NST45ED1 45,300 Grain Two Tank – Best Budget Pick
North Star NST45ED1-45,300GR Two Tank Water Softener
45300 grain capacity
1.26 cubic feet resin
18.6 gpm max flow
NSF certified
Pros
- Lowest entry cost among the two tank systems
- NSF certified for whole house use
- Rated for households of 1 to 6 or more
Cons
- Custom fit bypass may not match existing plumbing
- One owner reported repeated component failures
- Only three reviews to judge it on
The North Star is the cheapest way into a genuine two-tank system, and it is NSF certified, which is not something every unit at this level carries. It handles up to 45,300 grains and lists a maximum flow rate of 18.6 gpm, and the manufacturer rates it for households of one to six or more.
The warranty terms are the most generous on paper in this group. You get one year on parts, three years on the electronic control board, and ten years on the salt storage and mineral tank, which covers the two components most likely to be involved in a warranty claim.
It is rated for both city and well water sources, and the tank sizing is compact at 50 inches tall by 10.5 inches wide for the resin tank and electronics, with a 39 by 18 inch brine tank. That footprint is easier to accommodate than the full-size 10 by 54 inch Fleck cabinets.
The catch is the feedback. Three reviews is the smallest sample in the lineup, and one of them is a detailed complaint about brine tank, circuit board and float failures over four years of use. The other two report easy installation and good performance. We would treat this as promising but unproven, and we would not install it on a main house without a local service option.
Plan for the bypass valve
The included bypass is described as a custom fit unit, which means it may not drop straight into existing plumbing without adaptation. Confirm your line size and layout against the valve before you commit, and budget a plumber if the connection is anything other than a straight swap.
Check the 18.6 gpm flow figure against your household’s peak demand. That number is the maximum the system can pass without meaningful pressure loss, and a large house running multiple showers at once can approach it.
Where the value actually is
The value here is the two-tank format at the lowest entry point, plus NSF certification and a ten-year tank warranty. For a rental, a secondary home, or a household that wants continuous soft water without a large premium, that combination is genuinely useful.
The risk is the component failure report. Salt storage internals, the control board and the float are all replaceable parts, but on a lesser-known brand you are more likely to be ordering them yourself rather than calling a dealer down the road.
5. AFWFilters 64k Iron Pro Dual Tank with Fleck 9100SXT – Best for Iron
AFW Filters Built 64k Digital Dual Tank Alternating IRON PRO Water Softener with Fleck 9100SXT (3/4″)
64000 grains per tank
2 cubic feet
Fleck 9100SXT valve
Iron removal configuration
Pros
- Handles hardness and iron in one pass
- Targeted at homes of 5 to 7 people
- 10-year tank warranty with safety float brine tank
Cons
- 3/4 inch valve limits flow versus 1 inch models
- Very few reviews and no long term data
The Iron Pro configuration is the answer for well water that carries both hardness and dissolved iron, and this is the 64,000 grain per tank version of it. The dual tank alternates so one side handles iron-laden water while the other regenerates, which is exactly the situation where a single tank would put hard water through your fixtures.
A 10-year tank warranty and a large brine tank with a safety float valve assembly make this a complete installation rather than a partial one. The manufacturer sizes it for homes of five to seven people, which lines up with 128,000 grains of total capacity.
Two reviews, both five stars, is a promising signal and an unreliable one. We would never call this the most reliable system in the group on that basis, because two owners is not a durability record. What we will say is that the valve inside is the same Fleck 9100SXT used across the rest of this list, which is the part that matters most for long-term serviceability.
Also weigh the valve size. This model uses a 3/4 inch control valve, which constrains flow compared with the 1 inch variants. On high-demand households that is a real ceiling, and the sibling 1 inch version below is the better fit if you have the space.
When iron is the deciding factor
Ferric iron is the easy case. A standard softener handles it, though the resin will need replacing sooner in heavily ironed water. Ferrous or clear-water iron is harder, because it is dissolved and re-oxidizes inside the tank, which is where an iron-rated resin and a proper pre-filter earn their keep.
Our general well water softener guide goes deeper on distinguishing the two and on the filtration that usually sits upstream of the resin.
What to verify before you order
Get a real iron measurement, in ppm, before assuming this configuration is enough. Below roughly 3 ppm a standard resin with a softener iron filter handles it. Above that, you want to know what the system is rated for and whether your pre-filter is doing the heavy lifting.
Confirm your service flow needs against a 3/4 inch valve. If two or more high-flow appliances share the softener during peak hours, the narrower valve is where you will feel pressure drop first.
6. AFWFilters 32,000 Grain Dual Tank with Fleck 9100SXT – Best for Small Spaces
Fleck 9100SXT Dual tank water softener 32k, 32,000 grain with the digital 9100 sxt valve
32000 grain capacity
9 x 9 x 48 in tanks
170 pounds
Fleck 9100SXT metered valve
Pros
- Smallest footprint in the lineup for tight mechanical rooms
- Lowest grain capacity is the easiest to site
- Bypass and instructions included in the box
Cons
- Only one review and no reliability history
- 32000 grains may underserve a large home
Space is the constraint that knocks people out of the dual tank category entirely, and this is the answer to it. At 9 by 9 by 48 inches per tank, this is the most compact footprint in the group, and it lets you run a two-tank system in a mechanical room where a 10 by 54 inch cabinet simply will not go.
It uses the same digital 9100 SXT metered valve as the larger units, with metered on-demand regeneration to keep salt and water use down. The single owner review calls it very good value with noticeably softer water, and the box includes a bypass and instructions.
Thirty-two thousand grains across two alternating tanks is the smallest capacity we recommend, and it is the reason this is a specialist pick rather than a general one. It suits a couple, a small apartment, or a home with modest hardness and low daily use.
It ships at 170 pounds, which is the heaviest listed weight in the lineup despite the small footprint, so plan your install path and get help moving the tanks into position. Two full resin tanks do not get light even when the footprint is small.
Do the sizing math before committing
Multiply your hardness in grains per gallon by your average daily gallons used, then compare the result to 32,000 grains with a reserve margin. If your daily grain load approaches 800, this unit will be regenerating constantly and working harder than it should.
If the numbers come out close, step up to the 45,000 or 48,000 grain models instead. A slightly larger system in a room this tight is usually still easier to site than the alternative of running a regeneration cycle twice a day.
Where the tradeoff sits
You give up capacity and long-term proof. One review is not a track record, and at 32,000 grains you have less headroom for a growing household or a new appliance that raises daily water use.
In exchange you keep the two-tank benefit, the Fleck valve, and the smallest installation footprint here. For a small home with hard water and a tight mechanical room, that is a fair swap.
7. AFWFilters 48k Iron Pro Dual Tank 1 Inch Valve – Best for Higher Flow
48k Digital Dual Tank digital IRON PRO Water Softener with Fleck 9100SXT (1″)
48000 grains per tank
1 inch valve size
Iron removal 6-8 ppm
12 gpm service flow
Pros
- 1 inch valve gives more flow than 3/4 inch models
- Handles iron and hardness together
- 10-year tank warranty plus 5-year valve warranty
Cons
- Only one review and no long term data
- Same per tank sizing as smaller systems
This is the configuration we would pick for a household that needs both iron treatment and headroom for peak demand. It combines a 1 inch control valve with the IRON PRO alternating dual tank setup, rated for iron removal at 6 to 8 ppm and a service flow rate of 12 gpm.
That service flow figure is the number to look at. It means the system is specified to keep pressure steady while delivering up to 12 gallons per minute of treated water, which covers multiple high-flow appliances running at once in a home with moderate-to-high hardness.
The warranty package is the strongest in the lineup on paper. You get 10 years on the tanks and 5 years on the Fleck 9100SXT control valve, and the valve is the component most worth having covered.
One five-star review is the entire feedback base, so treat the rating as a signal rather than evidence. The valve is a proven design and the iron rating is specific and testable, which is more than you get from most thin-sample listings.
Why valve size matters more than most buyers think
A 3/4 inch valve is the default on many assembled systems because it costs less. On a house with a tankless water heater, a laundry that runs while showers are on, and a family of four, the difference between 3/4 inch and 1 inch shows up as pressure drop at exactly the wrong moment.
Compare the 12 gpm service flow here against the flow on the smaller-valve iron-rated model in this list. If your peak household demand is unclear, measure it or err toward the larger valve.
Know what this size does not buy you
Forty-eight thousand grains per tank is the same per tank sizing used by smaller systems in this category, so this is not a capacity upgrade over the cheaper units. You are buying flow and iron capability, not more resin.
If your daily grain load is high as well, look at the 64,000 grain per tank models instead and accept the larger footprint. Otherwise you will be regenerating frequently enough that the flow advantage matters less than raw capacity.
How to Size a Dual Tank Water Softener for Hard Water
Size before you shop, because the two mistakes people make are buying a system that regenerates several times a day and buying one so large that it never regenerates and the resin sits in saturated brine. Both waste money and both cause problems.
Step one: get a real hardness number. A hardness test strip or a lab report beats guessing. Water at 3.5 grains per gallon or above counts as hard, and anything above 25 GPG will need substantial capacity. Our general softener guide covers the testing options in more detail.
Step two: estimate daily gallons. A rough benchmark is about 75 gallons per person per day, which is what most sizing formulas use. Add more for a garden, a large family, or a household with a lot of laundry.
Step three: multiply for daily grain load. Daily grain load equals hardness in GPG multiplied by daily gallons. At 30 GPG and 300 gallons a day, that is 9,000 grains removed every day, and a system has to keep up with that continuously.
Step four: add reserve capacity. Size so each tank holds at least three days of demand, ideally more. On a two-tank system, one tank regenerates while the other serves, so per tank capacity is what sets your regeneration frequency, not total capacity.
Step five: check the resin type. Standard 8 percent crosslink resin is fine on chlorinated municipal water if you add a chlorine pre-filter. Ten percent crosslink resin resists chlorine degradation and is worth the upgrade on well water or on chloraminated municipal supply.
Dual Tank vs Single Tank: What Changes in Your House
The functional difference is downtime. A single tank softener stops producing soft water for roughly one to two hours while it regenerates, and during that window hard water flows to your showers, faucets and dishwasher. A two-tank system swaps to the second tank and regenerates the first, so the supply never drops.
Beyond that, a metered dual tank regenerates on demand rather than on a schedule, which typically cuts water use by 35 to 70 gallons per cycle and salt use by 25 to 40 percent when compared with older timer-based single tank units. Fewer regenerations also means less wear on the resin.
You pay for this in two ways: a higher purchase price, and a bigger footprint, since you need two mineral tanks plus a brine tank. For a home with a tankless water heater, four or more people, or hardness above 25 GPG, that tradeoff resolves quickly. For a single occupant on mild water, it is usually not worth it.
Installation, Valves and Long-Term Maintenance
Plan the space first. A two-tank system needs room for two mineral tanks standing side by side, a brine tank beside them, and a drain line that can handle regeneration discharge. The 10 by 54 inch Fleck cabinets are the standard footprint, and the North Star unit at 50 by 10.5 inches is the most compact option in this list.
Plumb the flow direction correctly the first time. The most common self-inflicted error in this category is installing the system backwards, and even a handy homeowner can make it because the bypass and the valve look similar from a distance. A homeowner who plumbed backwards still had to pay a professional to correct it, which is the argument for having a plumber do the connections on any system in this roundup.
Choose 1 inch line where you can. A 3/4 inch valve caps your peak flow, and it is a cheap thing to improve now and an expensive thing to redo later. Products 5, 6 and 7 above vary on this point, which is why we flagged valve size on each.
Watch for salt bridges. A bridge forms when salt in the brine tank cakes into a solid shelf above the water level, and the valve then cannot draw a full brine. Forum users report trying hot water, cleaning solution, and repeated regenerations, only to see the bridge return within a week. Keeping the salt level above the salt bridge line and using good-quality pellet salt resolves it more reliably than any cleaning shortcut.
Protect the resin from chlorine. Without a pre-filter, chlorine gradually destroys resin beads, and resin that would otherwise last 20 to 30 years may only give you 10 to 15. A whole house chlorine or chloramine pre-filter upstream of the softener is inexpensive and the single highest-return add-on in this category.
Service the control valve annually, check the salt monthly, and sanitize the system periodically. If you have a tankless water heater, treat the softener as a warranty requirement rather than a convenience, since manufacturers commonly require hardness treatment to keep the warranty valid.
Frequently Asked Questions
What are the best quality water softeners?
Quality comes down to the control valve, the resin volume per tank and the warranty terms rather than the brand name. Fleck, Clack and Autotrol valves are the professional-grade choices that most plumbers service and stock parts for, and they appear across nearly every reputable two-tank system. For dual tank setups specifically, the Fleck 9100 SXT is the most common valve in this category. Match grain capacity to your measured hardness and daily usage, and confirm the valve size suits your peak flow.
What is the recommended hardness level for a water softener?
Water at 3.5 grains per gallon or above is considered hard, and that is the point where softening starts to matter for scaling and soap performance. Above roughly 25 GPG you need substantial resin capacity or frequent regeneration. A dual tank system is worth considering above that threshold, or below it if your household runs multiple high-flow appliances at once.
What is the average cost of a whole house water softener system?
Professional-grade two-tank whole house systems with Fleck or Clack valves typically run into four figures, while entry-level two-tank units come in far lower. Add plumbing, fittings, a drain line and any pre-filtration to the equipment cost. Ongoing costs are salt, periodic resin replacement and annual service, and a metered valve reduces salt consumption noticeably compared with an older timer-based unit.
What are the best water softeners consumer reports?
Independent testing outlets tend to favor units with proven control valves and measurable hardness reduction rather than the largest capacity claim. For hard water, the systems that perform well share three traits: a metered demand-initiated valve, enough grain capacity per tank to avoid constant regeneration, and a documented serviceable valve. Check that the model you buy has independent hardness test results or a long enough owner history to judge.
What grain capacity softener do I need for a family of four?
Multiply your hardness in grains per gallon by your average daily gallons used, which is roughly 75 gallons per person per day. Then size each tank to hold at least three days of that load, since one tank regenerates while the other serves. A family of four at 300 gallons a day needs about 9,000 grains removed daily, so a 45,000 to 48,000 grain two-tank system is a sensible starting range.
Our Verdict on the Best Dual Tank Water Softeners for Hard Water
The DuraWater Fleck 9100 SXT 48,000 grain twin tank is the pick. It combines the valve most plumbers know how to service, resin that arrives preloaded in both tanks, and by far the largest owner base in this group, which is the only way to judge a whole house system responsibly.
Go bigger with the 64,000 grain per tank version if your hardness is extreme, add an Iron Pro configuration if you are on a well, and choose the 1 inch valve variant if peak household flow matters. Whatever you pick, test your hardness first, budget a chlorine pre-filter, and plan the drain line before the equipment arrives. That preparation is where most installs go wrong.