plumbingpump
Per the attached picture, I'm going to install a Grundfos comfort pump next to the solar hot water system. Supposedly it's half price on amazon, and it gets pretty good reviews.
My question is whether the Grudfos should be connected before or after the thermostatic mixing valve (which works great).
Also, given the tight spacing, any tips on the most efficient course of action in terms of cutting, elbows, etc.?
At the bottom is screen capture of the Grundfos Manual
Probably a failed/stuck/jammed check valve, if this was the typical (maketh me shudder) retrofit installation where the hot water recirculation line is the cold water line. That makes the proper operation utterly dependent on the check valve, or the cold water line can happily backfeed into the hot water.
The less-shudder-inducing system I prefer is a dedicated recirculation return line, but that can be hard to retrofit (and can have the same problem, if a bit less, since it normally returns to the cold side of the hot water heater.)
I'd prefilter (based on your other question calling this "ridiculously rusty water") ahead of your replaceable cartridge filters with a cleanable/dumpable screen filter (a vortex with a permanent screen in the middle and a catch chamber and dump valve on the bottom) between the pump and the pressure tank. That type of filter works best with fast flow.
In fact, I do on my own system. Put a bucket under the valve and it removes what's caught in the chamber and blows the screen clear (since the pressure tank is on the "clean" side of it.)
The cartridge filters will be better on the upstream side of the pressure tank (where they are now) since faster flow does not help them work better.
As for the plumber, sounds like "future plumbing work guaranteed" to me. So the plumber might like it that way - having fought a water softener with valves that got funky in a "rusty water house" I'm not in favor of dumping rusty water into one unfiltered.
Edit - if you WANT to rearrange your filters you could make some small argument for putting the activated carbon (taste and odor) after the softener, but it's a small argument and probably not worth the hassle. You might want to take off the "watering gardens" water before it and the softener, though.
This is the type of filter I use - "spin-down" or "vortex" or "sediment trapper" with a sediment trap below the actual filter screen. water enters and is spun around the outside at high speed, then drawn through the screen - a fair bit of the junk slides down the walls where it's thrown & falls into the trap and thus is not clogging the screen.
I use the 200 mesh (finest) stainless steel element, as I'm dubious about the longevity of polyester screen elements, which go finer. And I very specifically put it between the pump and pressure tank, which is not where the manufacturer suggests, but it makes the best engineering sense (since having the tank upstream means that dumping the sediment trap automatically backwashes the filter, & it does not have to be opened in normal circumstances.) If the water shed is not dark you might want to give it a box or a black bag over it to keep it from growing algae. Look occasionally and dump what it's caught.
Best Answer
I believe that Grundfos comfort system is comprised of two parts:
The pump is installed on the outlet of the hot water tank and the special tee fitting is installed on the furthest fixture in the house from the hot water tank. This special fitting bridges the hot and cold water supplies. The basic concept is that when the hot line is not in use, it will cool off. This special tee fitting allows the pump to pull the cooled off water in the hot water line back to the tank through the cold water line. This reduces the amount of wasted water that is poured down drain while waiting for hot water.
In your case, you are going to want to install the pump on the outlet (common port) of the mixing valve. This will allow for the proper loop to be created as well as to maintain the proper pressures on the valve as noted by UNECS.
As for advise on cutting the existing out, you're going to have to remove the entire portion from the wall back to the mixing valve outlet. It also looks like there is not enough room left on the pipe sicking out of the mixing valve to reconnect a new fitting to. You may have to sweat out the pipe and solder in a new piece, but be careful not to overheat the mixing valve as you will damage the internals. If you are going to be soldering the new pipework, keep in mind that the existing fittings that have been used are ProPress fittings which have a rubber seal inside of them (the bump in the hub) and that you need to be careful not to overheat them as well. In both cases you can wrap the fitting or valve with a wet cloth to help keep them cool.