3/4 Inch Hot Water Circulating Pump 3-Speed Circulation Water Pump for Solar Heater System(RS15-6 Red)

I installed this recirculating pump in parallel with smart Valve on my Tankless water heater to get hot water instantly by recirculating all cold water in hot water line. It feels great to have hot water instantly when you turn the tap during winter mornings. I save around 5 gallons of water every time I need hot water and this very much required in every home in So Cal where we have drought all the time.I installed recirculating pump at the hot water outlet on tankless water connected to a smart plug and at the far end of the house I used this smart value (https://www.amazon.com/gp/product/B08Q364CCZ) to connect the hot water and cold water line. When I instruct my google home to turn on the pump it will turn on the recirculating pump which in turn will open the smart valve. There is a timer which turns off the pump after 3 mins, which will in turn shut the smart valve. Initially I placed a Grundfos 595926 Valve in place of the smart value but its working intermittently and not perfectly.This recirculating pump and smart valve is a great addition and its running with no issues for last 4 months. We turn this system 5 to 6 times every day. I strongly recommend buying a Midline Valve EVGG0034-OM Dielectric Union Pipe Fitting (https://www.amazon.com/gp/product/B08L5QTHN2) which saved a lot of time with installation.

Definitely a nice pump. Very quiet and seems to be plenty powerful to get the hot water circulated.As some others have mentioned, the threaded are 3/4 straight thread. All copper threaded pieces are typically tapered (NPT). The way I got around this was to use dielectric fittings with a 3/4 FIP to 3/4 sweat ends. This does two things for you. One, it gets you the straight threads to get a good seal with teflon tape. And two, it allows you to totally remove the pump without having to cut any pipe.I run the pump using a smart plug hooked to my google home. I set up a custom routine so I just have to say one word and it runs the routine of "Turn on hot water for 1 minute" where the smart plug is named "hot water".

TLDR: The non-stainless version WILL rust; try different versions (and different "brands") of this pump if yours doesn't seem to pump enough water; ensure your pump comes with the pipe fitting adapters (that have o-rings) because the threads are NOT true NPT-fit threads and will leak; instructions are a joke so read enough reviews/do your own research to make sure you know how to install this (it's not complicated but the instructions make you question your own intelligence); no "on/off" switch so plan to use with a switched outlet or smart outlet for control.This review is for the unit I bought (RS15-6 Blue). I intended to use it with the Grundfos-made thermal bypass valve for creating a water recirculation circuit for my tankless water heater system. I saw several reviews that said this worked for people, but it was not always clear whether they had a tankless system or not. Tankless water heaters require a minimum amount of water flow to turn on (typically ~0.5gpm) and after plumbing this pump and the bypass valve, I discovered that I would only get about 0.3gpm through my water heater. I tried all the power settings on the pump, "bleeding" the air with the screw on the front and flushing the lines, nothing helped. "Bleeding" with the air screw did let out some spits of air/water but the way the o-ring seal is designed, there is no way to get it to seal again while the pump is running so beware of doing that and/or be prepared to get wet. I "knew" that the fittings were 3/4" MIP so I also bought all the associated hardware to plumb this into the existing copper hardline on the INLET to my heater (used SharkBite fittings + 3/4" coupling to a 3/4" nipple so that I could have something rigid to use for mounting with 3/4" pipe clamps). The installation was fine except that even with a more-than-typical amount of teflon tape, I was not able to get a leak-free connection between the coupling and the pump. I made the connections quite tight and I was worried I would over-tighten and crack something. I did make a simple plywood base to allow the flat sections of the pump to rest since my pipe situation would not support the pump on its own.Since the pump did turn on and wasn't overheating or making any weird noises (it was very quiet actually), I assumed that I was just out of luck since the Grundfos valve kit I purchased actually did explicitly state that it was not for use with tankless water heaters (though it said the reason was that it was not designed to be used with systems that had a water-return circuit). After a couple of days I uninstalled the pump again to see if I could figure out if there was something mechanically wrong, and that is when I saw the RUST in the pump. I was very disappointed to see that and also very upset that I potentially put my family at risk for having that in our drinking water system. I also read someone else's review about making their own parallel valve circuit with two Grundfos valves and additional hoses/fittings to allow twice the flow through the valves. So in a second round of attempting to get functioning water circulation, I bought all the pieces needed for making the parallel valve setup AND a stainless-steel version of this pump, but under a different name brand (BokyWok).Once I received the new parts, I first decided to just install the new pump and see if that would make any difference. I was surprised to find that there was actually an adapter in the kit that would connect to the pump with a 3/4" female O-RING fitting and then adapted to a true 3/4" NPT thread. I didn't end up using them, though, because I just tried to connect the SharkBite adapter hoses directly (the non-SharkBite end had a 3/4" female o-ring connector) and used some thick cardboard spacers to allow a standard 3/4" pipe clamp to secure the whole thing in place to my plywood base. After this simplified installation was done, I turned on the pump and the heater kicked on!! This was WITHOUT making any changes to the Grundfos thermal valve installation, and I was now seeing about 0.5-0.6gpm flow through the water heater.This has been installed for a couple of weeks and still working fine...returning the crappy pump I received and the now unnecessary additional thermal bypass valve components. Lots of small lessons here, but my biggest suggestion is to try at least a couple of pumps from multiple vendors if yours isn't working. I looked at many pumps and they all seem to be the exact same imported hardware with various branded stickers on them (including the "official" Grundfos ones).

Update: I've had this for 4 years now and still running great.Original review: I got this to circulate water from my hot water heater to the far fixtures in my house for instant hot water. It works great. Other reviewers posted issues with the pump because they couldn't stop the leaks from the connections. With a lot of plumbing experience, I figured that I was smart enough to overcome those issues. First thing to realize it that the threads are hose threads, not pipe threads so a straight pipe connection would not work. I first purchased an adapter with hose threads thinking that I had quickly whipped the problem - wrong, it leaked bad. I don't know if it was the weak threads or the adapter was warped, but after multiple tries I could not get it to stop leaking. So much for my superior experience. Next I tried a braided hose designed for water heater connections. That worked! The problem with this approach is how to support the pump because the hose will not. I got a long hose, 24", long enough to loop without kinking, and looped it so that the pump rested on top of the water heater. I used the styrofoam packing to cradle it and just let it rest on the water heater and completed the connection to the water supply with another braided line. No problems. I made a timer with a light switch timer linked to an outlet. That also works like a charm at less than $30. See photos. I am considering, however, getting a smart outlet so that I can turn on the pump with an app just when hot water is needed as another reviewer mentioned.