Jump to content

S traps

John Dirks Jr

Recommended Posts

Depends. If it's a historic home w/the old original lead trap, or some similar assembly, I point it out & talk about it, and get instructional. It goes in the report, but more as a point of information than being listed as a defect.

If it's a hambone remodel perpetrated by apparent mouthbreathers, I point it out as a defect. Even then, there are some variables that can make it work just fine.

Link to comment
Share on other sites

Originally posted by AHI

If you find S traps in older construction, how do you handle them? Do you just explain their deficiencies to the client an leave it at that or what recommendations do you provide?

I know in many cases it can be difficult to change them over to P traps. Can the addition of an AAV help prevent S trap siphoning?

My response to this same question that was posted in April:

There's a big difference between a real antique s-trap and bunch of spare parts that are put together to create an approximation of an s-trap.

Real s-traps don't siphon themselves dry; they never did and they never will. The men who designed them knew full well about the dangers of siphoning and they designed the s-trap so that an air break developed before the water could all siphon out. If you don't believe me, try it. You can't get a *real* s-trap to siphon dry. Siphoning is a phenomenon reserved for ersatz s-traps made from spare parts.

The real reason we did away with s-traps is subtler. If you've got a large slug of water moving through the drain system, it pushes a wave of high-pressure air in front of it. When this wave moves by an s-trap, the pressure is enough to cause the trap seal to "burp" and admit a small amount of sewer gas past the trap and into the room. (It takes remarkably little pressure to burp past 2" of water. You can try it yourself by taking a brand new p-trap, filling it with water and blowing through the waste end. The slightest breath will do it.)

The solution to this problem - the vented p-trap - allows the high-pressure air to dissipate out the roof instead of through the trap seal. Note that an AAV will not solve this problem. These valves only admit air; they don't vent it.

Proper old s-traps barely merit a mention in my reports. They're certainly not worth fixing.

- Jim Katen, Oregon

Link to comment
Share on other sites

Originally posted by inspecthistoric

One out of a couple thousand will actually siphon and it'll tell you it's siphoning. Just ask any plumber that's been at his gig for 3 or more decades (and isn't the type that needs to scare folks into spending more bucks while he's there fixing something else).

How would ever know which one your are inspecting is the "one in a couple of thousand?"

Unless you are a licensed Plumber, I would write up every one. Let the Plumber make the determination on whether or not the Trap needs to be replaced or reconfigured.


Link to comment
Share on other sites

I always mention them, I say they're no longer allowed, and I tell the client why, but I don't normally write them up as needing repair. I have yet to find one letting sewer gases in, and once clients know what the deal is they can determine for themselves if it's actually a problem or not. If I had one in my house and no gases were getting in, I wouldn't tear it out and replace it for no reason. Usually there are plenty of more meaningful fish for clients to fry.

Brian G.

Suddenly I'm Hungry for Hushpuppies [:P]

Link to comment
Share on other sites

Bear in mind: Given the existing labor pool, calling for repair/replacement of anything that's working OK right now will probably result in a worse outcome that just leaving the thing alone.

In the last couple years of my HI run, I told hundreds of customers that we're living in a time in which leaving well enough alone is the best way to go.


Link to comment
Share on other sites

Originally posted by randynavarro

So how does one differentiate between a proper old S-strap and a newer one?

You can still buy authentic s-traps. If you use them to replace antique ones, they'll work as well as the old ones did.

People sometimes approximate an s-trap by putting two p-traps together into an s-shape. These are bogus. No one knows how well they'll work. They certainly don't scour properly. They're wrong by any standard every written anywhere. Fake s-traps are easy to spot.

For those who persist in believing that an s-trap can siphon itself dry, go buy a real one and try it.

-Jim Katen, Oregon

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...