Seal caulk tubes with PEX cutoff caps

We have all been there.  I've tried many things over the years to prevent caulk from drying out in the tip of the caulk tube, from nails and screws to wire nuts, from various types of tape to the caps that come with some adhesives.  Some work OK, and some don't.  Inevitably it usually dries out in the tip, making it a pain to dig out the dried caulk so it will flow.

I recently re-plumbed the laundry room in a house we're renovating with 1/2" PEX, and I had a few scrap cutoffs that were anywhere from 3" to 6" in length.  They've been sitting in a bucket for a couple of weeks now because, to my knowledge, they are not recyclable in my area.  In the back of my mind I was trying to think of a way to reuse them before just dumping more plastic in the landfill. 

A few days ago I had finished doing some caulking, and I went for the pile of miscellaneous screws to find a 2-1/2 or 3" drywall screw to plug the tube - something that most of us have been doing for years without even a thought - when I caught a glimpse of the PEX bucket out of the corner of my eyes and (sound of brakes screeching) those would fit right over the nozzle!!!

I took one of the cutoffs and put it over the nozzle, and it had a nice tight compression fit that seemed like it would be air tight.  I stuffed a small piece of rigid foam (scrap from anther project) into one end, leaving about a 3/8" gap so I could squeeze a little of the caulk into the end to seal the pipe.

After checking the fit, I made a few more of them (the first one wasn't quite as neat as the next few).  I put my new "cap" onto the caulk nozzle, pushed it on tight, and left it overnight.

When I checked it the next morning, the caulk on the end still wasn't completely set up all the way through.  I took it off the caulk tube carefully to see if it sealed well, and the caulk came out of the nozzle just as well as when I put it away!

I left it alone over the weekend, and when I checked it again the caulk was still fluid at the tip! So far I think it works really well.  If it does indeed work for long periods of time, no more digging dried caulk out of the tip!

Follow up:

After over a week the caulk is still fluid at the tip and required no poking or cleaning to use!  I'll leave the last bit in the tube and leave it for an extended period to see how well it does, but if you're going to use the tube within a week or two, it seems to work.

Notes:

The caulk I did this experiment with was an Acrylic/Latex "painter's" caulk (DAP Alex 25 yr with the green writing).  It does not adhere well to the inside of the PEX tube, and if you push it with your finger it will move.  It still seals the tube, but I'm going to make some with a silicone caulk or adhesive next time I'm working with it.  Maybe that will stick better to the PEX.  

What you'll need:

1. A piece of 1/2" PEX tubing 3"-6" long.
2. Caulk/sealant - Silicone or Acrylic/Latex plus Silicone will probably work the best.
3. Small piece of foam or something to stuff in one end to form a backer for the sealant.

Instructions:

1. Stuff your backer material in one end of the PEX tube, leaving 3/8"-1/2" at the end for the tube for the sealant.
2. Apply sealant to the end of the tube and let dry for 24-48 hours.
3. Press the open end of the PEX tub over the tip of the open caulk tube, making sure the fit is snug.