How to Connect a Hose to an Indoor Unthreaded Faucet
Many indoor faucets do not have a thread on the inside or the outside. They also come in a wide variety of shapes and designs. This is great for fitting in with your design style, but can be a challenge when it comes to using fixtures and fittings. For example, there are many reasons why you may want to securely fit a hose to an indoor tap.
In my particular case I use the hose most often to fill my aquariums, but it can also be useful for plants and hydroponics, to attach small appliances, for cleaning, and many other applications. It was surprisingly difficult to get a tight and flexible attachment that would work on an indoor tap, but this is what I learned:
Option #1: A Lever Adapter
One type of adapter uses a lever to press the tap down onto a rubber ring, to create a tight seal. The best example of this is probably the Koala faucet adapter. The main limitation of this design is that it only works for a faucet with the 90 degree angle at the end, and within a small range of diameters. For a faucet that is exactly the right design the seal is reasonable good, but can still leak under higher pressures. This type of adapter is one of the more expensive options; typically around $20-30.
In my case none of my indoor taps was the right design. One was too wide, one was too square and the other had a broad U-shaped bend rather than a 90-degree angle. So the major limitation of this design is that it does not work with most tap designs.
Option #2: A Reflexed Rubber Fixture
A very common option is a flexible rubber bell that folds internally to try and create a flexible seal that will fit range of taps. There are two limitations to this device. One is that it fits a smaller size of hose. So attaching this to a longer, standard-sized garden hose can be challenging. The other is that they tend to leak at even the lowest water pressure. This might not matter match inside a bath tub, but over a sink or any other surface you will tend to get water everywhere other than where you want it. I attempted to get a better fit hose-clamps and other devices, but none of these efforts was very effective.
Option 3#: the Water Bandit
Ultimately the best option turned out to be the Camco Water bandit. This fitting is flexible enough to avoid leaks even at higher water pressure. And the range of taps it will fit is wide, due to a stepped funnel shape. This fixture has a standard thread and so will attach to any water hose and allow your hose attachment to be as long as you need!
Adding a Hose Clamp
I found the water jack alone was very effective, but if you ave a small or odd shaped faucet or very high water pressure you might want to also use a metal cable tie--the type that is tightened and released with a screwdriver. These can be sourced cheaply at any adware or auto-supplies store. This will assure a good water-tight connection. But remember not to get a usual-size hose clamp as this fixed with be considerably wider in diameter. You want something that will clamp onto 1.5 times the diameter of your faucet's outside surface.
Having tried all three products the Water bandit is a clear winner on all four important criteria.
1) It fit my tap and would fit a very wide range of faucet designs.
2) It is compatible with standard threaded garden hoses.
3) It does not leak even at high water pressures.
4) It is also the cheapest option at just $6!
Hopefully my expense and experiences can save you time and money in solving your own indoor watering needs and applications!