Water test of new DWV w/ toilet having integral cap

[Tbbarch]

I am preparing to water test the new PVC sewer and vent lines for a new bathroom.
The toilet has a knock-out flange built into it.

Is the knock-out flange suitable for holding water during a water test?
If so, when I fill the system won't there be an air pocket in the toilet arm of the line?

If the knock-out flange will hold, my solution is to drill a hole and insert a screw to plug it allowing me to bleed out air as the system fills.

Insight please.

 

[Jeff H Young]

yes it will trap air. sometimes I bleed it off sometimes I don't on ground work I usually bleed air

 

[Sponsor]

 

[James Henry]

I suggest you leave it alone. Bleed the air from the stand pipe Jim caps. Nothing worse than a leaky flange during an inspection.

 

[Tbbarch]

I suggest you leave it alone. Bleed the air from the stand pipe Jim caps. Nothing worse than a leaky flange during an inspection.

I have never heard of a Jim cap.
The air is trapped in the pipe up to the toilet and that is adjacent to and not the same as the sewer stack.
I only know of standpipes in relation to fire suppression and this is residential sewer.

 

[James Henry]

The pipes you stub up through the concrete for your plumbing fixtures. A jim cap is a rubber cap you put on the stub ups for a water test.

 

[wwhitney]

Maybe I'm missing something, but I don't see the air pocket as a problem. The air will still be pressurized by the weight of the water above it. If you're worried about it, you could leave the test on for 24 hours; that would convert all but the slowest of air leaks into a water leak. Or you can listen closely at the air pockets for hissing, or use a soapy solution leak detector on those areas.

Cheers, Wayne

 

[Tbbarch]

Maybe I'm missing something, but I don't see the air pocket as a problem. The air will still be pressurized by the weight of the water above it. If you're worried about it, you could leave the test on for 24 hours; that would convert all but the slowest of air leaks into a water leak. Or you can listen closely at the air pockets for hissing, or use a soapy solution leak detector on those areas.

Cheers, Wayne

Wayne-toilet flushes down, then goes horizontal or to vertical discharge. Water flows down, air rises up.
The toilet flange being sealed traps air that can not rise up into where the toilet will sit.
I am really am going to avoid listening for an air leak.

 

[wwhitney]

I'm thinking the only air pocket would be in the vertical section between the closet bend and the closet flange. Is there an allowable geometry that leads to a larger air pocket?

If you don't want to listen for air, then you could just spray the two joints at the top and bottom of that closet riser with a leak detection solution.

Cheers, Wayne

 

[James Henry]

Fill the system up with water the day before your inspection let it sit for 30 minutes, if the water level goes down look for a leak, if there is no leak top off the water level again and wait, the water will push any air out and eventually turn into a water leak. At some point the water will compress any air that is trapped and your water level will be stabilized. You only need to hold the water test level for 15 minutes to pass an inspection, the key is to test your system a day before the inspection for leaks and observe how it holds the test when there might be some air trapped somewhere. In preparation for a drainage rough in test a plumber will fill the system up and leave it for hours until the inspector shows up and then he will top it off, and he has already confirmed from his own testing that it will pass.

 

[Jeff H Young]

as long as there no leaks topping off as soon as inspector rolls up is usually good. the screw in the cap not always seals but some rubber under screw head might help. I'd avoid bleeding off there as well

 

[Terry]

I have never worried about air below a closet flange during a test. I used to plumb five homes a week, and that was never a worry.
I love that the new closet flanges come with built in caps. When I started out, we had to glue the test caps ourselves. And then worry that the cap would hold the test.