How does the Ella dual drain speed up draining a walk-in tub?

Ella's Dual Drain Technology speeds up draining by giving the water two oversized paths out of the tub instead of one, and by letting air in as fast as the water leaves. Most Ella walk-in tubs have two independent 2 inch gravity drains, each on a four-port T-type body, with drain dials that double as air vents and no pump anywhere in the system. How Fast Do Walk-In Tubs Drain and What Speeds It Up? gives the drain times and the plumbing choices. This page takes the drain apart piece by piece to show why each part makes the tub empty faster, and what it means when yours is slower than the published figures.

Two Drains, Two Paths Out

A conventional tub has one drain. Most Ella walk-in tubs are built with two independent 2 inch gravity-driven drains, two overflows and two openers, so the water leaves through two paths at once. Each drain is operated on its own with a large dial opener fitted with an extender for an easier grip and turn, and each dial moves a stainless steel cable with a lever that opens or closes its floor drain. Open the first drain and the tub empties at a fast pace. Open the second and it goes faster still. Two drains with two openers are also a layer of safety, because if one drain should ever clog, the other still empties the tub. The floor drain covers are height adjustable for optimum sealing and draining, so a cover set correctly keeps a full tub full while you bathe and releases cleanly when you open the dial.

Size is the other half of the speed. The industry standard drain size is 1 and 1.5 inches, and a standard house bathtub drain is 1.5 inches. An installer who has fitted competing tubs puts it in plain terms: a 2 inch pipe carries about four times the volume of water of a 1.5 inch pipe, and Ella uses two of them. The water flows straight down through the two 2 inch openings and out, so the speed comes from the size of the openings and the pull of gravity rather than from anything that can wear out.

The Four-Port T-Type Body and the Air Vents

Under each 2 inch floor drain sits a T-type body with 2 inch ports, four ports in total on a dual-drain tub. The video on this page shows how the house drain can be connected to all four ports for maximum draining capacity, or to either side, with the ports not in use sealed off. Connecting two of the four ports is common, and connecting all four gives the fastest gravity flow. The T-type layout is also what lets the drain be vented properly and release air pockets, which is what makes the water move out with less resistance.

Water cannot leave a pipe faster than air can take its place. The easy turn drain handles are also dual air vents, and the dual drain itself works as a vent system, allowing fast air pocket relief and drainage. The dual drain doubles the air vent capacity, so air pockets are relieved rather than fighting the outflow, and the tub keeps draining steadily to the end instead of slowing as the water level drops. The same dials function as overflow protection at the same time.

Gravity, Not a Pump

Because the system is gravity driven, there is no pump and no electricity involved. It keeps draining at full speed when the power is out, which matters for a bather who needs to get out, since a pump or power failure could significantly slow the drain process and prevent you from exiting quickly. Powered drains can be faster on paper, but they put stress on house plumbing and stop working when the power goes out. The trade-off is that gravity needs a fall. The house drain must sit below the tub outlet, and draining into a washing machine box or any drain higher than the tub calls for a pump arrangement instead, a decision to settle with your installer before the tub is set in place.

What the Published Figures Mean

Three figures appear in Ella's material, and they describe different conditions. Ella's field test of the dual drain, shown in the video on this page, completed drainage in 52 seconds under Ella's own conditions. The published figure for an average tub is about 80 seconds under ideal house-drain conditions. And the figure to plan around at home is two minutes or less once the tub is connected to a proper 2 inch drain line. Everything between those numbers sits on the house side of the drain, because the tub's part of the job ends at the T-type body, and Drainage and Fill Time pairs that drain with a faucet fill rate of about 16 gallons per minute.

Why Your Tub May Be Slower Than 80 Seconds

If your tub takes much longer than the published figures, check these in order:

• Each drain handle turned all the way open. Clockwise opens and counter-clockwise closes, until it stops. If one side drains and the other does not, check the second handle.
• How many ports are connected. One port still works, two is common, and all four is fastest.
• The branch line the tub ties into, which should be 1 1/2 inches to 2 inches, with a 2 inch house main recommended for the fastest emptying.
• A Y fitting rather than a T, and the fewest elbows possible, since water changes direction less. There is roughly 3 inches of clearance under the tub for 2 inch PVC, so the run can go to either side.
• The condition and venting of the house drain. An old, clogged or poorly vented house drain is the most frequent reason a new tub drains slowly, which is why Ella asks for it to be tested for free flow before the tub goes in.
• A stopper that is not sealing or lifting fully because its locking nut or height needs adjustment.

The sewer main is not on the list. A tub on a 3-inch sewer line drains about as fast as one on a 4-inch line, because everything downstream of the 2 inch connection is already larger, as Will a 3-Inch Sewer Line Make My Walk-In Tub Drain Slower Than a 4-Inch Line? explains. The full step-by-step for a tub that drains slowly, will not drain, or loses water while you bathe is in Tub Drains Slowly, Will Not Drain, or Loses Water: What to Check.

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