‘Homemade’ Copper Cap Water Block

Detailed pics to build your own very inexpensive waterblock. — Owen Stevens.

Well, since the last success with my water block creation, I was getting a bit antsy about doing some more experiments. I had an idea to make a water block from a copper cap, some copper bar stock, and tubing.

OK, I think I got the idea from a copper cap water block I saw a while ago (Surlyjoe’s “Beehive”), but I did have what I consider an original improvement for it!

I figured that with a higher internal volume and an inlet that sprayed directly on the core, it would work pretty good. Here are the raw materials:

  • A 1 ½ inch copper pipe end cap
  • Some 2″ x 1/8″ copper bar stock
  • A piece of 1/8″ copper tubing

The nice part about this is that the caps cost $1.50 at a plumbing supply store and 1 ft of 1/8″ tubing was only $1.98 at good ol’ Home Depot. I had the bar stock left over from the 2 ft piece I bought for my last project.


First I drilled a hole in the cap for the inlet with my trusty drill press.


The hole was just big enough to fit the copper tubing.


I drilled another hole for the outlet.

Hole 2

The idea is that the inlet will spray water right on to the core as aligned here. I left about a 1/8″ gap. The outlet will be at the ‘top’ of the cap so the cap fills with the sprayed (and hopefully swirling) water.

Hole 2

The next step is to hold the tubes in the cap correctly while I solder them in. I used my long needle nose locking pliers and vise.


Here it is after soldering sitting on my vise to cool.


Here I am showing the inside. You can see how the inlet tube will be close to the core and the other at the ‘top’ (Note: I have on heavy leather gloves because the copper had to be hot enough to melt the solder – hot enough to cook my hand to well done!)


I needed to align the center tube with the core and center of the base so I drew some pencil lines to set it up. The base is 3.25″ x 2″ bar stock. I then drilled the attachment holes.


Here is a dry fit before base attachment.


To make sure the cap is flat, I filed it down – that’s why it’s shiny here. I also filed the base smooth to ensure a good solder grip.


Here it is soldered together.


Finally, I leak tested it by sealing one tube and blowing into the other. I use this test to look for bubbles. I also attached it to my hose outside to see if it can withstand water line pressure.


Here is the final product, bottom lapped and polished up with some fine steel wool. Steel wool is great for polishing copper but doesn’t really remove deep scratches as will lapping .


This block worked OK but it wasn’t the great improvement I was looking for. My temps were the same as with my first ‘homemade’ block. This block was very easy and quick to make, though – only about 2 hours work. I hope this helps some of you out there who want to make your own water block.

Oh yeah, I almost forgot – I attached it using the four mobo holes in the same way as my previous water block with bolts, rubber backed washers, springs and some wing nuts.

Owen Stevens

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