what exactly meets the definition of a "non-positive shut-off" as required for the on/off control on the shower spray unit per 2010 ADAS 607.6?
Paul L. Bishop, Architect
Original Post
Non-positive as in must hold pressure on a lever or button (similar to some hose nozzels), "positive" on/off positions similar to a light switch.
I did a lot of research to attempt to understand this about a year or so ago, and am racking my brains to remember it! I started by googling it, and was able to find helpful groups in the plumbing industry who explained the term. It has to do with a safety measure, and makes sense, but on first look, it seems almost to be contradictory! I'll continue racking my brains, but maybe someone will know the answer much sooner.

OK, so ADA guy is already there, as I found when I posted this. Yes, it's a means for controlling the water, and I believe it has to do with not getting scalded, but again, still racking my brains.
607.6 Shower Spray Unit and Water. A shower spray unit with a hose 59 inches (1500 mm) long minimum that can be used both as a fixed-position shower head and as a hand-held shower shall be provided. The shower spray unit shall have an on/off control with a non-positive shut-off. If an adjustable-height shower head on a vertical bar is used, the bar shall be installed so as not to obstruct the use of grab bars. Bathtub shower spray units shall deliver water that is 120°F (49°C) maximum.

I wonder how someone takes a shower in the fixed position? They have to hold the switch the whole time?
It can have both. The issue is if you are using it as a handheld and the water is on all the time it will "wiggle" all of the shower and spray everything. The idea is that you have to be able to be using it such that you can release the "switch" and the water doesn't necessarily continue to run.

Also remember hearing hearing at the ANSI Committee meeting something about the water must also not completely shut off such that the pressure builds up and when you turn it on a large force is created to blow the water wand away or out of the person's hand.
Yes, Bradley, I did do this research in connection with ANSI, in order to vote on it. I remember the valve had to do with safety, so maybe it was pressure. Unfortunately, I didn't keep notes on it. I just remember starting my research thinking it sounded like some kind of "made-up" word, since "non" and "positive" seem like opposites to me!
Paul, they used the term they used, because that is the industry term as far as I understand it. I think it's important to use industry terms when you want to communicate with industry!
Paul, the difference I have noted is similar to the difference of a French hand held shower which is a constant on constant off vs the ADA on when held down and off when released.

Pressure buildup is not usually an issue unless local water pressure is excessive, in which case use of a pressure regulator is advised.
oh my, i may have misunderstood the requirement.

are you saying the water out of the hose does not come out, until the user is pushing down a button or control? and then flow stops when that control is released?
Originally posted by BrentWiese:
oh my, i may have misunderstood the requirement.

are you saying the water out of the hose does not come out, until the user is pushing down a button or control? and then flow stops when that control is released?

The shower spray head should have a non-positive shut off valve so that when they let go, it will turn off.
although i see the value of the ability to turn off water at the hose end, i don't like this.

from what you describe, then to have water, the user must hold down the button. that requires grasping and continuous pressure. for me, that would be uncomfortable, and for some users not possible.
Point well taken Brent but this is a case where DOJ did not seem to have considered requiring the controls not to require manipuliple digits.

They seem to have assumed that users would have the ability to pinch and grasp (or have an aide?).

I believe that the term refers to a handheld valve that makes the shower head continue to dribble water when the main valve on the wall is left on.  This maintains positive water flow pressure so that water in the head and hose cannot backflow and siphon dirty tub water into the fresh water supply line if it is dropped into a tub with standing water.  Remember that the hose has to be at least 59" long so it would fall to the floor of the tub if dropped.   It's a plumbing safety requirement.

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