How to Cap a Water Valve or Fitting Without Leaking

When doing repair work or renovations in your kitchen / bath you might need to use a cap for a water valve or fitting. This comes in handy when you have a leaky valve or want to keep you main water valve on while removing a faucet / fixture. This video will show you a proven method to make a robust seal between the standard 3/8 compression cap and the compression water valve or fitting. If only the compression cap is used you only get a metal on metal seal which can be prone to leaks.

Parts Used

Tools Every Weekend Warrior Needs

DISCLAIMER: This video and description contains affiliate links, which means that if you click on one of the product links, I’ll receive a small commission.

[BaresarkSlayne]

2 years after initial posting, this is a life saver! I'm trying to remove a dishwasher and we have this hard water that has messed up the valve, so I can't shut it off all the way, it just keeps trickling. I picked up a coupling with the idea that I would use a cap to stop it, but metal to metal, even with plumbers tape makes sure that it never seals. It's in the way of doing some kitchen remodeling and it's been frustrating. It's also a huge waste of space because we don't even own enough dishes to fill a dishwasher and the fact that it takes hours to do the job just makes it useless when we could remove and replace it with additional base cabinets for storage, which we are short on. All so we can get a new modern fridge, then countertops.

[gm-truckin]

Thank you!!! I bought exactly what u linked from home depot to cap off an old dishwasher that we don't use anymore the supply line was leaking so I took it off and just capped it using your method! it is working great and after searching the internet for awhile this video is the only thing I could find even closely related to what I needed to do!

[jackio]

I LOVE it when I type a question in the search box and immediately find a video with the perfect solution to my problem!!! Thanks so much for your help!!! 🙏

[cghn]

Exactly what I was looking for, I purchased two end caps, both of them leaked,
I was trying to shut off two pipes that where connected to a mixer tap.
All the Teflon tape in the world would not stop them from leaking.
After watching this video problem solved, brillant🙂🙂🙂🙂

[emilys]

Thank you for this! I’m trying to remove a small counter and sink from my laundry room. I’m not ready to pay a plumber to come and fully remove the water line so I’m capping it and nothing was stopping the dripping. This is such a simple fix to an incredibly frustrating issue I was having and your video and explanation are perfectly done

[borndiy]

You did just what I needed to know. I already bought the CompressionCap. Thinking on flat-2-flat surface going to leak. Checked here & found you. Just need the washer. Dishwasher line from sink but will still be using hot water for sink. Wanted to leave faucet handle as it was in case of future having another dishwasher. My DIY for inlet water line from 2-Companies sending me wrong hose. Gave up and decided to cap line. Thanks for your help and know I'm now sure to have no leaking...YAEH!!! Florida

[EJ-zneo]

Its just amazing so many people have this same issue to solve. Thank you for the help. I didn't know about the washer trick. My caps kept leaking and I was trying to figure out how to fix that.

[antwinettenicole]

Wow! I was having a problem with the valve leaking and just came across your video! I went to Lowes, immediately, and showed them your video. They had, originally, had me try the tape. However, it was leaking. So, I bought the washer and so far, no leaking. God Bless you for making this video! 🙏

[ES-bnbi]

I just removed an old dishwasher which I do not wish to replace, and your video perfectly demonstrated how to cap the water supply line. I went to the hardware store and got the supplies you recommended and they worked. THANK YOU!

[markw]

Thanks for the video. My intuition told me that a rubber washer or o-ring was needed to help seal since that's how the hoses are constructed, but the guy at Ace swore up and down it was not needed. Sadly, I took his advice and of course it leaked. Your video confirmed what I suspected. The links to the parts are very helpful. Headed to HD now...

[rybfish]

Thank you! This is exactly what I needed to find out how to do it. I got the parts at Home Depot and it worked out perfectly. Cheers!

[sca]

Scott, I really appreciate the tip. I came upon your video by accident as I was looking for instructions on how to replace the entire compression-type shut-off valve under the bathroom sink due to a leak from a cap I just installed. My shut-off has two outlets, one of which was being run up into the attic to supply an Aprilaire humidifier to the second floor furnace that I have removed with a new furnace installation. It's a bad idea to have a water supply running to an attic in the Midwest where temperatures drop well below freezing, but that's another story.

Anyway, I disconnected the copper water line running to the attic and capped the second outlet only to have an annoying little leak. I was probably accumulating a few drops of water per day in the bucket under the cabinet. This rubber flat washer did the trick and saved me from having to replace the whole valve. You tip saved me a few bucks and some time working under the sink in a tight place. Much thanks!

[DougPoulton]

Ace didn't have the 35063B washer so the guy at ACE told me to use a brass ferrule. I told him that didn't make sense because metal to metal will still leak. His response was quit watching youtube. Then I saw you had the washer with the Home Depot part number so that's where I went. Thanks.

[heckyesitsjess]

This is what we are doing on a t that doesn't need to be used under my sink in an hour because it's got a slow leak. This brings me solace in knowing it's going to work to add the gasket, and I can cancel the 100 to 175 dollar plumber bill. Thank you so much!

[johnpratt]

Fantastic tips! I've got a bathroom demo with a toilet shutoff valve that doesn't quite shut off all the way, so I can't remove it yet to rip out the floor. With this info I can get a cap that will seal off the last bit of dripping water without waiting for a super-busy plumber to come in.

[vikingnorth]

Thanks, your tip worked great. I had to cap off the angle valve from the wall until I get a new dishwasher. I used a Danco 00 flat washer in the cap, and have no leaks.

[mrwyz]

I had never had a weeping compression cap so this was driving me crazy looking for burrs and corrosion. You saved a lot of tools being embedded into my walls a ceiling. Thank you.

[bobbymuse]

Very helpful video. Thank you for helping me end this long day of driving back and forth to the hardware store.

[matthewr]

Thanks so much for this, got hints from 2 plumbers and both told me to use the 1/4 cap with teflon tape and you will be fine. Could not stop the cap from leaking. Saw this and verified Lowes had the 1/4 inch zero flat washers in a Danco assortment pack. Got it home and the 1/4 inch rubber washers would not fit inside the cap. What else could go wrong? Cut the washer in small increments until it fit, tightened a bit but not too, turned on the water. Small leak was fixed by tightening a couple turns. Should have listened to my wife when she said yesterday, google it, look on youtube. Thanks again.

[imacexpress]

Really appreciate this video. I watch you regularly but missed this at some point. Searched and boom! Really appreciate you humor too. I love the “space under the cabinet” too. Really cozy lol