# Jim caps



## dmar2053 (Feb 6, 2013)

Does anyone know what pressure Jim caps start to blow off at?


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## rjbphd (Feb 5, 2010)

dmar2053 said:


> Does anyone know what pressure Jim caps start to blow off at?


 What's a Jim caps???


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## plbgbiz (Aug 27, 2010)

rjbphd said:


> What's a Jim caps???


Slang for Benji cap, which is slang for Benjamin cap, which is slang for rubber test cap.


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## crown36 (May 21, 2013)

dmar2053 said:


> Does anyone know what pressure Jim caps start to blow off at?


 You can use them for testing-- if that is what you're getting at. Apply 5 PSI into your system and you're good to go. Make sure your bands are at 60# I do not advise ever using a jim cap when testing water supply/distribution. Hope this helps.


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## dmar2053 (Feb 6, 2013)

We have to test with water. Inspector makes us and its a nightmare finding a leak with air. I have a 54 unit apartment building I'm roughing right now and really don't want to spend the money on glue pressure caps for every lav and kitchen. I have about 35ft of head pressure and I know that's a lot of pressure on the first floor. I was just curious if there is an actual rating on the caps.


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## Corvette Mark (Nov 19, 2013)

What we usually do is duct tape criss-crossing over the caps as well as nailing a 2x4 over the toilet flange test plug incase of blowouts. However you are correct to look for a rating on the cap what ever brand Fernco etc. A quick phone call would be a safe bet if not printed on the cap itself. I would imagine you are testing in sections and not all at once?

I also would price the cost of jiffycaps vs cost of glue caps.


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## wyrickmech (Mar 16, 2013)

Jones caps is a brand name here we call them j caps. If you have a tall building and are worried about blowouts just air test 5psi of air will not cause any problems at the base of the risers


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## Turd Chaser (Dec 1, 2011)

We call them mission caps or fern I caps. Again based off of manufacturer


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## shlomy81 (Apr 23, 2012)

We use caps that's called test caps it's a cheap glue in cap hold 7 psi no problem even water 8 story's high,


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## wyrickmech (Mar 16, 2013)

shlomy81 said:


> We use caps that's called test caps it's a cheap glue in cap hold 7 psi no problem even water 8 story's high,


if it is 8 story's high it is a lot more than 7 psi. We used to use those glue in test caps we quit after one blew off and caught a man in the forehead.


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## MTDUNN (Oct 9, 2011)

Triplecrown24 said:


> You can use them for testing-- if that is what you're getting at. Apply 5 PSI into your system and you're good to go. Make sure your bands are at 60# I do not advise ever using a jim cap when testing water supply/distribution. Hope this helps.


I glue a wafer cap then a Jim cap


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## Letterrip (Jul 28, 2013)

wyrickmech said:


> if it is 8 story's high it is a lot more than 7 psi. We used to use those glue in test caps we quit after one blew off and caught a man in the forehead.


That's scary!!


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## shlomy81 (Apr 23, 2012)

10 years never blow off


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## Redwood (Sep 8, 2008)

They will blow off whenever they damn well feel like it....

Last winter I was sent out one night for a cap that blew off a frozen roof drain line on a 1 story building...


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## MTDUNN (Oct 9, 2011)

Redwood said:


> They will blow off whenever they damn well feel like it.... Last winter I was sent out one night for a cap that blew off a frozen roof drain line on a 1 story building...


If you glue a wafer cap then a coupling over it and the Jim cap. Wouldn't that suffice?

Edit : won't work for no hub though obviously


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## Redwood (Sep 8, 2008)

MTDUNN said:


> If you glue a wafer cap then a coupling over it and the Jim cap. Wouldn't that suffice?
> 
> Edit : won't work for no hub though obviously


I didn't give it much thought, it was 11 pm in a electronic games store and the roof drain was pouring inside the store from the melting snow on the roof...

I just put it back on tightened back up with my Seekonk put a couple of hose clamps I stole off of some large Ferncos around the tee and cap, crossed my fingers...

Then I told em sit tight I'm going to get the jetter and I'll be right back to open this line up...

The jetter blasted through the ice in the line pretty quick and their problem was over... I took my hose clamps back...


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## MTDUNN (Oct 9, 2011)

Heh at least you got them back


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## RW Plumbing (Aug 16, 2010)

I find it depends on the pipe size for when they blow off. Bigger pipe, less pressure it takes. Don't forget psi stands for pounds per square inch. The bigger the surface area the more total pressure the caps exposed too. 

On 6-8" caps 5 psi might be too much, where 35-40 has no effect on 1 1/2".


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## Redwood (Sep 8, 2008)

RW Plumbing said:


> I find it depends on the pipe size for when they blow off. Bigger pipe, less pressure it takes. Don't forget psi stands for pounds per square inch. The bigger the surface area the more total pressure the caps exposed too.
> 
> On 6-8" caps 5 psi might be too much, where 35-40 has no effect on 1 1/2".


I'll agree with that! :thumbup:

It was an 8" cap that blew off in the store I was talking about.

Figure 10 psi on a 2" cap has a total force of 31.5 lbs on it.

An 8" cap with the same 10 psi has a total force of 502.5 lbs on it. 

She's gonna blow! :yes:


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## wyrickmech (Mar 16, 2013)

Redwood said:


> I'll agree with that! :thumbup: It was an 8" cap that blew off in the store I was talking about. Figure 10 psi on a 2" cap has a total force of 31.5 lbs on it. An 8" cap with the same 10 psi has a total force of 502.5 lbs on it.  She's gonna blow! :yes:


 you haven't see nothing blow until you see a 18 in test ball go. Now that will make you crap your pants right there!


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## Redwood (Sep 8, 2008)

wyrickmech said:


> you haven't see nothing blow until you see a 18 in test ball go. Now that will make you crap your pants right there!


I think my best blow was a 24" line draining an over filled pond that I jetted...

That was a step back moment when the line cleared....:laughing:


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## wyrickmech (Mar 16, 2013)

Redwood said:


> I think my best blow was a 24" line draining an over filled pond that I jetted... That was a step back moment when the line cleared....:laughing:


 the test ball was on a steel roof drain outlet that spilled into a concrete spillway. The test ball was three feet above grade. It blowed out on a water test with a lot of energy behind it. The building had 40 feet clear to the bottom of the bar joists. The test ball crossed a ten acre field bouncing and spinning with a flood of water behind it. The most interesting was watching the water. Until it lost head pressure it wasn't hitting the ground for twenty to thirty feet.


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## Plumbus (Aug 4, 2008)

Had a long test ball blow and soak an inspector. Couldn't understand why he wouldn't sign the card.


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