S-trap thermal image shows water level is OK

Help Support Plumbing Forums:

JamieRI

Member
Joined
Mar 30, 2020
Messages
22
Reaction score
1
Location
Wakefield, RI
I wondered why my kitchen's S-trap has never smelled or gurgled.

Tonight I filled my sink with hot water:
1586064580489.png

and opened the plug to let it drain.

Then I waited 10 minutes and took the visible and thermal images below:

1586063996779.png1586064084780.png

This shows me no siphon is happening with my sink. I think there are two reasons I am getting lucky: 1) The sink basket is pretty constrained and the water runs down quite slowly. Here is my strainer.
1586064336233.png

And the other is this drain meets the horizontal drain in my basement perhaps 14" below the floor
 

Attachments

Diehard

Well-Known Member
Joined
Aug 19, 2017
Messages
2,640
Reaction score
468
Location
North Reading, Mass.
I'd guess it was the strainer reducing the flow rate enough so it's not filling the pipe completely.

Still not approved on new work. Of course existing stuff doesn't get inspected.
 

breplum

Professional
Professional
Joined
Nov 14, 2017
Messages
360
Reaction score
138
Location
Lafayette, CA
I do not think the image shows "no siphoning". If that were the case, it would be red above the trap.
I think that all the warm water drained except the expected slug remaining in the trap, as is proper. It just still has residual heat, which will cool over time.
BTW, you have a direct dishwasher connection which should be rerouted to a dishwasher air gap.
And certainly you should add an air admittance valve on that improper S trap.
Is that thermal imaging done with the $224. iOS attachment or something higher grade?
 

Mitchell-DIY-Guy

Well-Known Member
Joined
Oct 16, 2019
Messages
144
Reaction score
44
Location
North Carolina
For many years, S-traps were perfectly legit. Then they were not. Many if not most of the time, they work.

There are cases then they don't and that's why the code changed from S to P. But, that doesn't mean ALL S traps failed by siphoning the trap water...
 

JamieRI

Member
Joined
Mar 30, 2020
Messages
22
Reaction score
1
Location
Wakefield, RI
S traps not approved anywhere as far as I can tell.

I remember how I loved how the upstairs bathroom sinks would drain in the antique house of my childhood: fill the sink, and it would start pulling so hard it would create all kinds of slurping sounds!

Breplum wrote:
"I do not think the image shows "no siphoning". If that were the case, it would be red above the trap."
I think that all the warm water drained except the expected slug remaining in the trap, as is proper. It just still has residual heat, which will cool over time."

Jamie: Exactly! I waited several minutes for the plastic to cool before taking the image.

Breplum wrote:
"BTW, you have a direct dishwasher connection which should be rerouted to a dishwasher air gap."
Jamie: How about if I move it to the dishwasher port on my garbage disposal that was more recently installed? I would punch out the slug to open it up. I would also support the hose up under the counter. (Frodo coached me on this here)

Breplum wrote:
"And certainly you should add an air admittance valve on that improper S trap."
Jamie: Yes... Frodo described how to put install P trap with AAV in the same post. I haven't bought the parts yet.

Breplum wrote:
"Is that thermal imaging done with the $224. iOS attachment or something higher grade?"
Jamie: It is Seek Thermal CompactPRO once found Refurbished on Amazon. Normally > $400, I found it refurbished at $264, but now shows Not Available . It plugs into my Android phone, and there iOS models too. I wanted the higher resolution model for better images of hot components on circuit boards. Lower resolution models would be fine for images such as the one I posted.

Thanks for your help!
Jamie
 
Top