Installing Thermostatic Mixing Valves & Recirculating Pumps in Plumbing Systems

Guest speaker Julius Ballanco, P.E. and acclaimed plumbing columnist, describes how to properly install hot water recirculation systems that incorporate protective thermostatic mixing valves. He begins by giving an overview of the importance of scald protection, then moves to an overview of the various types of mixing valves available, their intended uses, and their corresponding ASSE rating. Using a unique technique of showing a series of piping schematics from simple to more complex, Julius describes the various components needed to allow consistent temperature delivery including check valves, balancing valves and temperature gauges and their proper placement and adjustment.

[@SuperBushfan]

Hi guys. I have an issue where hot water is somehow creeping into the cold supply line. We run a 75gal heater with a circ pump, and simple balancing valves in the showers. Not sure how or where we'd get the crossover of hot water into the cold supply line (and vice versa), but this seems to be what's happening. Any thoughts as to how to trouble shoot and correct? Many thanks!

[@CaleffiHydronicSolutions]

Thank you for your comment. The situation you described can happen from the induced flow of a pump. Therefore, we offer our thermostatic mixing valves with flow checks on the hot and cold inlets as an option. We also offer flow check tail pieces which can be retrofitted into existing installations to solve this creep flow. Please check with your local supplier for complete details or feel free to contact us if required.

[@SylvanTieger]

Julius is brilliant

[@CaleffiHydronicSolutions]

Thank you!

[@ErnieOlszewski]

i turbulence an issue in dropping water temps with recirculation pumps

[@moundhir09]

what if the flow of the water return is less then the cold water supply, the cold water goes to the water return then what?

[@CaleffiHydronicSolutions]

moundhir eclip If the return water flow is less than the cold water supply, then the return and cold water will mix at the tee near the mixing valve cold inlet, as desired. Take another look at the video, around minutes 40 to 44, for an explanation of the importance of the check valves, globe valves, and pressure balancing to assure proper flow direction. We hope this helps.

[@moundhir09]

yes i know it will mix xin the tee but the flew direction will not go to the return ? lets say we have 2.5 bar pressure coming from the cold line and 1 bar from the return, did the cold water goes to the return direction?

[@sweetvuvuzela4634]

This video is very old no mention of fail safe here in the U.K. the valves shut off the hot side if the cold side fails and hence no chance of scalding

[@CaleffiHydronicSolutions]

Thanks for your inquiry. The information contained in the video is for the North America audience.

[@sweetvuvuzela4634]

@@CaleffiHydronicSolutions thanks too much 🤗

[@mrmuscle4354]

Looking at the diagram it looks like the hot water line is on the right side but to my understanding it should be in the left side

[@CaleffiHydronicSolutions]

Mr Muscle thank you for your question. The diagrams are for illustration purpose only. Our mixing valves are marked with a red dot for the hot water inlet; therefore the valve can be turned over so the red dot for hot water inlet is now on the left side. Hope this helps.

[@jaimegutierrez1585]

I can not understand this. Why would the tempered water even be connected back into the mixing valve like this? it would make more sense to loop the tempered water back way closer to water heaters cold inlet line and put a back flow device behind the tee. Wouldn't that turn the cold supply to the mixing valve into a dedicated line with no tempered water and eliminate the creeping problem?

[@CaleffiHydronicSolutions]

Sorry for the delayed answer. If 100% of the recirculation water was returning to the storage tank, then the tank heater would have to work harder (more energy usage) than if only a portion of the recirculation water was returned to the storage tank. To maintain the recirculating hot water at the desired delivery temperature, the heat lost from the loop must be replaced. This requires some water flow between the loop and the hot water source. Ideally, this flow is adjusted such that the rate of heat transfer from the hot water source to the loop exactly balances the rate of heat loss from the loop’s piping. We hope this helps, otherwise contact us! www.caleffi.com/usa/en-us

[@davec3487]

I agree. Why not just return to the hot water tank and avoid all of these creep issues. I see the response below but it makes no sense. How is the boiler working harder just because you are returning water to it. A BTU is a BTU.

[@michaelarones4530]

Cold water is only drawn into mixing valve when there is faucet usage. When there is no usage and with the "tempered" recirc run directly back into the tank's cold-in, re-feed to loop from tank's hot-out quickly raises to loop to the temp of the tank. When faucet is turned on, you then get scalding water for however long it takes water to flow from mixing valve to that faucet (could be several minutes). The scenario is for when you want the tank to have legionaire killing water temperature in a recirc loop environment.

[@WABoothPlumbing]

Yeah that's alot. It's easiest to do a recirc pump with at source mixing valves. That's a disaster waiting to happen with all those tees and check valves

[@CaleffiHydronicSolutions]

When piped properly the recirc pump will pump through the mixing valve, meeting minimum flow requirements and ensuring stable domestic water supply temperatures eliminating temperature creep in the system.