DESIGNING SAFE WOODEN HOT TUB SUCTION FITTINGS
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Wood tubs can be a lot of fun and are very pleasing to look at. However, just like swimming pools and spas (or any device that people use), they need to be built with all the safety measures that we know about today. Many of the older designs are now deemed unsafe.
According to the ANSI/NSPI
8.0 RETURN INLETS AND SUCTION
8.2.2 A minimum of two (2) suction outlets shall be provided for each pump and the suction outlet system, separated by a minimum of three feet (3) [91.44 cm] or located on two (2) planes; i.e., one (1) on the bottom and one (1) on the vertical wall, or two (2) separate vertical walls. These suction outlets shall be plumbed such that the water is drawn through them simultaneously through a common line to the pump.
This is about a simple as
pie". You can change the spices in the pie, but you can't leave out the
"apples and the crust". You must, by these rules of safety, separate
the suction inlets and have two on each jet pump. The fittings have to
be ANSI/NSPI and UL safety suction fittings as well. They must be sized
for the volume of water
that is expected to go through them. (The FPS of water flow per Sq. IN
exceed the limits.)
If you examine the human body it is easy to see why it is important to separate the two suctions and the need for two suctions.
A single pumps can create quite a bit of vacuum, some over 20 inches of Mercury, enough to trap and hold a human being on the bottom of a wood tub. This is particularly true with young children, since they tend to panic easily and do not have the physical strength to fight against even a 1/2 HP pump's vacuum.
As long as there are two suctions with NEVER THE POSSIBILITY off both suctions being covered by the torso of one person's body, the design is safer.
If someone is drawn onto one of the suction inlets, the second suction will offset the vacuum and allow easy escape.
The design must account for all possibilities including having both suction covers removed or broken. If you find an open suction without the screened cover, do not use the spa or hot tub!!
Any design where the suctions are closer than three feet of each other and on the same plane, or on the same level as in the bottom of a wooden hot tub is potentially dangerous. (See drawing A below).
If you examine the torso of the human body, the average length from one's seat to one's shoulder is about 26 inches in a normal sized adult. From the back of one's head to the seat is about 36 inches maximum distance.
The idea behind the three foot rule is so that if both suctions are open (with face plates missing or broken) a normal human being's torso will not cover both suctions at the same time. That is why you must design in the three foot rule (or greater as in The Spa Specialist wood tub instructions). (In our instructions we tell our customers to place the two suction fittings on two separate planes and more than three feet apart, so that if both suction fittings are open, it is absolutely impossible for any human body torso to even be able to touch them at the same time.)
We also never instruct anyone to place a dynamic inlet on the bottom of the wood tub (or acrylic spa). That is not proper to do, because in the fittings are made of plastic and are much easier to break compared to the metal grates or heavy plastic grates often used in swimming pools. (We have found that children, particularly teenagers, will have "horse play" in spas.) The body weight is much heavier when you can stand up as in a wood tub. If the suctions were at the bottom of a pool, they would be more difficult to break.
The manufacture does not recommend having them on the floor, because they are designed to go on the wall. They are not designed to walk on. As this terrible use of wall suctions ages, it can leave the suction fitting with no covering. That means that a small child with long hair will have the hair swirled into a "rope" and sucked into the plumbing lines. YOU MUST NOT USE A WALL FITTING ON THE FLOOR EVER! The proper place for a wall sution fitting is on the wall where bathers cannot stand on it. The only allowable floor suction fitting is called a "swimmming pool main drain". It is a minimum of 12 inches in diameter and has to be installed in pairs of two at a minumum of 3 feet apart.
Much of the old fashioned designs were a copy of old swimming pools, and do not have the advantage of all the information we have now on spa and hot tub safety.
So, if you are a person with children, or are simply concerned about your safety, never buy a spa or use a wood tub made without all these safety rules in place. Completely disregard their instructions if they do not conform to safety standards. (Don't buy a tub from someone who disregards the ANSI Standards)
You have to remember that many
times these tubs are transferred in ownership, and there are no safety
instructions left to the new owners. That leaves them vulnerable, due
to absolute ignorance on the disasters that can be caused by a poorly
designed tub. The tub should be safe in all areas and in all
circumstances that can transpire.
A good example of HOW NOT TO BUILD A WOODEN TUB plumbing system is shown below. In the drawing it shows the suctions closer than three feet apart and on the same plane. These are also wall fittings, not designed to walk on , mounted on the floor where they can easily be broken. There is only one company in the US that makes a wood tub suction fitting that I know of. I placed one on the floor, and it broke immediately when I stepped on it.
If you have a tub with this design, or anything similar,
you need to change it immediately to conform to the ANSI, and the
manufacturer's instructions on the fittings. At any moment it can
become very dangerous, if the cover fittings break. If the seller
provided "wall type" suction fittings they cannot withstand the normal
foot trafic of a hot tub without breaking. (Any of the floor type of
pool drains, which are appropriate for this use, have at least four
screws and are nearly flush with the floor. The
real floor suction, main drains, have the ability to take the full
weight of people without breaking.)
8.2.3 " A minimum of (1) suction outlet and (1) skimmer shall
be provided for each filtration system"
A skimmer is a device that draws water from the very top of the spa water line. It pulls in the surface debris.
In the above drawing, do you see a skimmer in the wall?
I have never seen any quality pool or spa installation that did not
have a skimmer.
I believe that in order to have a clean water in the tub, you
to skim the debris off of the top. Even if it was not a
requirement of the ANSI, it simply makes sense to skim the surface of
floating debris. Take a look at all the hot tubs and spas and
tell me how many of them do not have a skimmer of some type?
If you need help with how to fix this or how to re-plumb it call 1-888-478-2224. Just tell the person on the line that you have a defective wood tub suction system and are in need of instructions on how to fix it. We also have the parts you need as well.