Obviously, the Ford cut in tee the OP referenced is the ideal solution and by far the simplest to install. But it ain't currently available, and no one else makes a similar fitting. So, what's the OP to do? Just say screw it, I'll go without water since the code sez blah blah blah about underground solder joints? As with a lot of things in business, sometimes you have to improvise and not worry about the code.
People who've never been in the piping business can't fathom the fact that a lot of the codes were written when the only soft solder in common use was 50/50 and the average plumber didn't have a clue about how to make a silphos joint. Once written into the code, things tend to go on the theory that whatever was good enough for Grandpaw in 1945 is the only way to do it today.
I would use silphos to make the joints, but that's because I have $500 worth of Turbo Torch and B acetylene cylinder that I doubt the OP has, nor does he want to buy for one job. One thing I should have mentioned in the previous post is to use Stay Brite #8 solder and Stay Clean flux to make the joints, as it is strong, lead free, and easy to use without the requirement of a high temperature torch.
I ran into a situation a few years ago where an improperly cleaned joint had been made with some unknown soft solder on a 410A air conditioning system. Due to the location I had no faith in being able to adequately clean the soft solder out of the joint so I could make it with silphos. So I emailed Harris to find out if Stay Brite had adequate strength for the pressures involved with 410A refrigerant. One of their engineers responded that it would be fine, and included pics where they had done tensile tests on Stay Brite joints showing the product exceeded the strength of the tubing and would actually tear the tubing apart before the solder would fail. Harris is also a major producer of silphos, so it wasn't a case of them recommending their product over a competitor's product, but rather just a simple case of Yes, this product will work for that application. If it has enough strength to tear the tubing before the joint fails, there's no logical reason to assume it has inadequate strength to hold an underground water line together.
It's interesting that some people are afraid of a properly made solder joint underground while the same joint in a wall or above a ceiling can cause thousands of $$ of damage if it fails. The only thing an underground failure causes is some mud, work, and inconvenience.
