How to fix leaking gutter end cap – In just 5 minutes for $10

By Tom •  Updated: 08/22/22 •  5 min read

For the longest time, I had a very slow but steady drip coming from the gutter end cap above my deck. The angle of the gutter is a bit off so it tends to pool water at that end – that’s a repair story for another day. 

The problem was that the seal on the gutter end cap had eroded away. Prolonged exposure to the elements can degrade sealants and caulks that will eventually cause cracks and leaks. I didn’t need to replace the whole thing just re-seal it up. 

(Some of the below links are affiliate links which means I get paid a bit if you click through and buy something — it doesn’t add anything to your cost! Just helps keep the lights on.)

If you have a leaking gutter end cap you’ll have to do one or more of three things to fix it: 

  1. Apply a sealant – if the end cap itself is intact and not damaged
  2. Repair the end cap – if the end cap is bent out of shape but is in good enough shape to fix up and reapply sealant
  3. Replace the end cap altogether – if the end cap is rusted or too badly damaged to fix with sealant.

Chances are you’ve got aluminum gutters with crimped end caps. If so, here’s what I did that ended up working great, it took 5 minutes and cost $5: 

What is the best gutter sealant to use on end caps?

Before you start you’ll need to decide on a sealant or caulk to use.

Criteria to consider when buying a sealant:

gutter sealant for a leaking end cap: osi gutter GS121
I’d recommend using this gutter sealant for a leaking end cap

Here is what I used that worked great: OSI Gutter and Seam Sealant GS121 (Buy from Amazon (Affiliate link) or Home Depot) If you’re just fixing one or a few gutter end caps you probably don’t need a large tube of it that requires a caulking gun. With this you can just squeeze it out manually, it works on aluminum, galvanized, and vinyl gutters but it does take 7 to 14 days to fully cure, so keep that in mind:

OSI GS121 Gutter and Seam Sealant White
Click Here for Lowest Price
We earn a commission if you make a purchase, at no additional cost to you.

How to seal leaking end caps on gutters

If the gutter end cap that is leaking is still structurally intact, is not rusted out, doesn’t have any holes int it, and is not completely bent out of shape, you should be fine simply applying a bead of sealant to the area rather than replace the whole thing.

How to Fix Bent or Dented Gutters (Solved!)

Tools you’ll need: 

  1. Grab your trusty ladder to get up to the trouble spot – make sure you follow our guidelines for leaning a ladder against gutters and be safe about it!
  2. Inspect the end cap – is it damaged beyond repair? Rusted? Are there holes in it? If yes to any of these, you’ll want to look into replacing the end cap altogether. Mine looked okay from the outside, it was really just the seal between the end cap and the gutter.
inspect leaking gutter end cap
  1. Remove any previous sealant – I just used work gloves and a putty knife to scrape it out. See the section at the bottom for why it’s all black in there….
  1. Clean the entire area off, inside and out around the gutter end cap – get rid of all debris, leaves, dirt.
  2. Make sure it’s all totally dry and dust and dirt free
  3. Use a hammer or rubber mallet to tap the end cap in place to make sure it’s firmly seated
  4. Make sure the end cap is tightly crimped on by taking pliers and squeezing around the edges
  5. Put a bead of gutter sealant along the inside seam of the end cap, all the way from one end to the other. Wet your finger so the sealant doesn’t stick to your finger then run your finger along the bead to make sure it’s in the gaps and smoothed out
It ain’t pretty but it worked
  1. Let it dry – check the sealant you’re using, but it should take at least a day or two before it’s sufficiently dry and able to withstand the elements. Best case is if you can do this work before a dry spell during mild temperatures.

Here’s how NOT to fix a leaking gutter end cap: why should you use a gutter sealant?

The first solution I tried seemed promising and was really just a quick thing I tried without much thought behind it. I took a spray-on rubber sealant and sprayed the hell out of the inside of the end cap. I thought for sure that would hold for a while given how much I sprayed in there. 

But alas, it didn’t work. After a couple of months it started leaking again. Turns out given all of the standing water, it eroded the seal of the spray on stuff and created a channel underneath it. 

So I ended up stripping it all out and using the sealant instead. 


A few years ago I bought my first house. It’s 100 years old. It’s clearly had a history of less-than-professional DIY handymen/women. And APPARENTLY you’re supposed to actually put work and money into it if you don’t want it to look terrible or water to rain down on you while you’re sleeping. About YouTube Facebook Twitter Pinterest Instagram