Delta faucets feature either the famous (or infamous) ball valve, which the company invented, or a cartridge valve, which has become more or less standard in faucets everywhere. When a Delta faucet leaks, you can easily fix the problem by either replacing the gaskets around the valve or the valve itself. However, this presupposes you can access the valve and that means removing the handle. Actually, this is quite easy to do — or is it?
Where Is the Set Screw?
The handle won't come off on its own; you first have to loosen the set screw holding it to the valve stem. If you have trouble locating the screw, you're not alone. The company purposely places it in a location on the handle where you aren't likely to notice it and hides it behind a decorative cap. Find the cap and you've found the set screw.
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On a lever-style handle, which you'll find on most single-handle Delta faucets, the set screw is directly under the lever, and you may have to crouch down to find it. On some upscale Delta kitchen faucets, the screw is on the side of the handle cover that's facing the back wall when the faucet is off. This introduces the added complication of having to turn the water off before you can rotate the handle and remove the set screw, but you have to do that anyway if you're servicing the valve, so, no biggie.
Once you find the cap, you may be mystified by how difficult it looks to remove. Don't worry, because all you have to do is pry it with a flat-head screwdriver, and it will pop right off. Be careful, though, because it's small and can easily get lost down the drain.
Use the Right Allen Key
"Great," you think as the cap comes off, "now all I have to do is loosen the set screw with my Allen key," and you poke in the standard 1/8-inch key that most homeowners have in their toolset, and it won't fit. That's because Delta has thoughtfully provided many of its faucets with 3/32-inch hex screws, and you need an Allen key of that size to turn one. You may have a folding set of metric Allen keys, and if you do, this is approximately 2.5 millimeters — not exactly, but close enough to do the job.
Allen keys have an L-shape, and the short part of the "L" usually fits easily in tight places. If you have a folding Allen key set, though, you may have to rotate the faucet to get the key into the hole. This problem occurs mostly with single-handle faucets, and you can often rotate these with brute force, as long as you remember to rotate the faucet back into its original position when you're done. If the faucet won't turn, put your folding set away and go to the hardware store to buy the right size key.
The Set Screw Won't Turn
You have the right size key and room to work, you insert the key and the screw still won't turn. Try a little harder, but don't overdo it, because if you strip the screw head or the thin and fragile Allen key breaks off inside it, you'll basically have to cut the handle off or pry it with a crowbar. More likely, you'll have to replace the faucet.
Remove the key, get a can of WD-40 with the red spray tube, insert the tube in the screw opening and give the screw a few squirts. Wait at least five minutes before trying the screw again. No luck? A couple more squirts followed by another five-minute waiting period should do the trick.