Hot water recirculation question

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Jetboy55

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Doing a full bath remodel in master bathroom. Replumbing the master bath with PEX-A and will be making some additions and changes around the water heater so that there are shut offs for the two main branches in the house, and adding flex lines to the water heater input/output, since it's hard plumbed copper right now (which means I can't easily replace the anode at the input line. So, since I'm doing this work, I was thinking of adding in hot water recirculation for the master bath branch, and for the kitchen branch. But planning and plumbing everything to include hot water recirculation is going to take this novice a lot longer, causing a delay in getting started, and upping the possibility of me making a mistake, so I was considering the following..........
Since there are just two main portions of the hot water plumbing, one goes north to the kitchen, and one goes south to the master bathroom, I might install a simple under sink recirculation in the two locations. I have always on power available under the kitchen sink, and I can install an outlet under the bath sink easily during remodel. Will these simple under sink recirculation systems provide decent performance? I just want to cut down the hot water time from 50 seconds to something like 10 seconds, during daytime hours. I can use a smart plug for timing, ect... to turn it off at night. The runs to each location are about the same at approx. 40 feet in a single level ranch home. Thanks for any advice.
 

John Gayewski

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Yes they will work fine. They pump hot water intuitive your cold water so there's a concession there with that.

The best most trouble free way is recirculating lines back to the heater with a pump and in your case balancing valves. Not sure how the money works out on these two ways to do it, but I personally don't want the under sink pumps. To each there own. Some people will probably say have had them for years and they work great, but I think generally they are kind of cheapo systems and pumps.
 

Jetboy55

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Thanks for the reply. I originally wanted to do the centralized way, but when I was looking up how to do it, it seems pretty complicated, what with pressure balancing, bleeding requirements, expansion tanks, check valves, ect.... Thats why I started to think of doing it the way I mentioned.
 

John Gayewski

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Thanks for the reply. I originally wanted to do the centralized way, but when I was looking up how to do it, it seems pretty complicated, what with pressure balancing, bleeding requirements, expansion tanks, check valves, ect.... Thats why I started to think of doing it the way I mentioned.
While you are remodeling I think I would do the recirculation lines if I could. You could likely set up those under sink pumps to pump to recirculation lines also, I haven't thought about that system of operations very much, but having the lines is better than not having them, you don't have to use them.
 

Jeff H Young

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Totaly agree with John, on the 2 type systems , Ive installed both and Obviously a properly planned out pipping arraingement with dedicated return line is an awsome system you will love (at a price) The Cheapo system you might be pretty happy with as well , evedently youll need 2 of those systems for the cheapo system.
My home is on slab I thought about running the undersink one many times just havent done it , also thought about running a half inch line from a hot line near the master back to water heater . but that wont help my kitchen a bit
 

Tuttles Revenge

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A dedicated return line is the way to go if you have the walls open. And while not the proper way of handling balancing, a ball valve will do it. You're basically creating resistance on the side with the least resistance til they're balanced.

There are 2 types that don't use a return line. Both pull water from the tank and dump it into the cold water side til the aquastat is satisfied.
1 where the pump is at the water heater and there is a bypass valve located under a remote fixture like the sink.

2 where the pump and cross over are placed under the sink itself.

I'm not certain how having 2 locations might affect performance with the crossovers. I've never installd them that way, only single locations.
 

John Gayewski

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Navien's Navi circ system allows up to two pumps. We are doing a job (with my strenuous objection) with about 40 pumps, one in each apartment. We'll see how that goes, but Navien says not to. It's a long story about why we are doing this so don't ask.
 

Jeff H Young

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Ive only used circuit setter ballancing valves any valve works I would think just not well and long term I think a poor choice
 

Jetboy55

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Thanks all. After a little more looking, it looks like I can install the Watts Comfort system. The pump is at the water heater outlet, and two aquastat valves go under the sinks, one under master bath sink, and one under kitchen sink. The pump deadheads against the valves all the time, unless the timer has turned it off. Then each valve opens and closes as needed when the water cools down at each sink. It sounds like that will work just fine for my simple two trunk system. I imagine I can forgo the mechanical timer, turn the pump to "always on" mode, then use a smart plug to fine tune the times for the pump to be on giving hot water to my lines.
 

Jetboy55

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I did install the Watts system, and it's been about a month. I can say I'm very happy with it. Even though there is no return line, it still gives me very warm water within 3 seconds, and hot water within 10 seconds. That's way, way better than the 1 minute it used to be. The mechanical timer on the pump is what I'm currently using. It is very granular, allowing for multiple on/off transitions per day, I've never seen this type of mechanical timer. So all is good in my house and thanks for the help.
 

DrBoom

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were you able to insulate your lines during the plumbing effort in support of this recirc pump? We just installed the Watts system using the mixing valve at the endpoint (actually, I installed the taco valve since it was way better reviewed) and I'm quite surprised at the heated water drain on the hot water tank. If I leave our pump on, we burn ~12 gallons of 104F water per hour. That's nearly as much as my heat pump water heater can recover excluding any actual hot water usage.

Our path is quite long - nearly 150 linear feet from the water tank to the furthest faucet which has the valve on it. That's ~3.5 gallons of water in the (mostly PEX) pathway that rapidly cools. I now have the pump on very minimally so it doesn't burn all of our hot water. It takes about 20 minutes for the pump to heat the line all the way.
 

Fitter30

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Only two types of valves for balancing circuit setter or globe valve in the bottom out the top. With such low flows would downsize the valves at least one size.
 

Jeff H Young

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Im glad you like it ! my hot goes from water heater in garage up to the attic of a 2 story home then back down a wall in the kitchen underground about6 feet to kitchen sink its easily more than a full minute for hot or even warm water
were you able to insulate your lines during the plumbing effort in support of this recirc pump? We just installed the Watts system using the mixing valve at the endpoint (actually, I installed the taco valve since it was way better reviewed) and I'm quite surprised at the heated water drain on the hot water tank. If I leave our pump on, we burn ~12 gallons of 104F water per hour. That's nearly as much as my heat pump water heater can recover excluding any actual hot water usage.

Our path is quite long - nearly 150 linear feet from the water tank to the furthest faucet which has the valve on it. That's ~3.5 gallons of water in the (mostly PEX) pathway that rapidly cools. I now have the pump on very minimally so it doesn't burn all of our hot water. It takes about 20 minutes for the pump to heat the line all the way.

20 minutes for the water to get hot on the farthest outlet? so you are calling it a terrible waste of energy?
 

Jetboy55

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My trunks are all 3/4, pex-a to master bath, copper to kitchen and1/2 bath. Both runs are about 50 feet in opposite directions. I haven't insulated yet, but I am certainly going to soon.
 

Jeff H Young

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Jetboy, glad its working well, I actually concidered 2 as well my kitchen and master are spread apart and it takes a long time for hot house is on a slab and dont want to bust open walls. but not happening soon just thought about it a long time.
 

DrBoom

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Im glad you like it ! my hot goes from water heater in garage up to the attic of a 2 story home then back down a wall in the kitchen underground about6 feet to kitchen sink its easily more than a full minute for hot or even warm water


20 minutes for the water to get hot on the farthest outlet? so you are calling it a terrible waste of energy?
For our purposes, it means that using the pump needs to be carefully timed to match usage. If we just turn it on for a couple of hours around the time we anticipate using hot water, or run for 20 minutes an hour or something to make sure we have hot water all the time, the usage is so high that the heat pump water heater won't be able to recover from any usage. The cost of that energy usage given how efficient the heat pump water heater is, is not a problem. The burn rate making the recovery of the tank nearly impossible is more significant. That was not something I anticipated before installing the pump.
I suspect our extra long runs are uncommon. 150' of water in PEX pipe cools very quickly in our 62F house.
 

DeeKay

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My Watts system seems to be acting strangely. I have the crossover temp-sensing valve under the kitchen sink returning through the cold line, about 70’ run through interior walls from the AO Smith 40 gal paired water heaters. The pump is activated by a smart switch on voice control and when “Hot Water ON” is asked for I will get warm and then hot water at the sink within 1-2 min. That all works as expected, though I am not crazy about the lack of cold water available when the pump is running.

Lately I have noticed that, with the Recirc pump Off, I can run the hot side for over 3 minutes and never get above lukewarm with intermittent slugs of noticeably colder water in the flow. I don’t have a clear idea of how those slugs of cold water get into the flow. I understand that the cold -> hot crossover is open when the Recirc Pump is not pushing 95deg+ water to the crossover, but what flow scenario allows cold water to show up in the hot side of that Hot Watr tap (adjacent to the crossover at the most distant point in the plumbing run.)

When I test the crossover with the Recirc pump off, the cold angle valve off and the cold tap On, I get an extended flow of lukewarm water for around 3-4 minutes before the flow reduces. The flow never completely stops but reduces to more than a trickle but less than a “stream.” Does that suggest that the crossover valve is not operating properly?

On a side note, I am trying to understand where the pressure/flow is relieved when the pump is running. As the cool/warm water in the long hot side is pushed toward that crossover valve to the cold run, where does that water go and how is the additional pressure relieved?

thanks for any illumination on how this system is supposed to work !
 

John Gayewski

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My Watts system seems to be acting strangely. I have the crossover temp-sensing valve under the kitchen sink returning through the cold line, about 70’ run through interior walls from the AO Smith 40 gal paired water heaters. The pump is activated by a smart switch on voice control and when “Hot Water ON” is asked for I will get warm and then hot water at the sink within 1-2 min. That all works as expected, though I am not crazy about the lack of cold water available when the pump is running.

Lately I have noticed that, with the Recirc pump Off, I can run the hot side for over 3 minutes and never get above lukewarm with intermittent slugs of noticeably colder water in the flow. I don’t have a clear idea of how those slugs of cold water get into the flow. I understand that the cold -> hot crossover is open when the Recirc Pump is not pushing 95deg+ water to the crossover, but what flow scenario allows cold water to show up in the hot side of that Hot Watr tap (adjacent to the crossover at the most distant point in the plumbing run.)

When I test the crossover with the Recirc pump off, the cold angle valve off and the cold tap On, I get an extended flow of lukewarm water for around 3-4 minutes before the flow reduces. The flow never completely stops but reduces to more than a trickle but less than a “stream.” Does that suggest that the crossover valve is not operating properly?

On a side note, I am trying to understand where the pressure/flow is relieved when the pump is running. As the cool/warm water in the long hot side is pushed toward that crossover valve to the cold run, where does that water go and how is the additional pressure relieved?

thanks for any illumination on how this system is supposed to work !
There is no extra pressure. These pumps don't work like that. It's more like a ceiling fan moving water, the fan throws the air and the pumps throws the water but it doesn't actually pump anything.

It does sound like your crossover valve is bad. This is actually not a great way to recirculate water, but if it's your only option it's OK.
 

DeeKay

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Thanks ! (I’m not sure ceiling fan analogy quite works since the moving air is not contained…)

I understand that the Recirc without a dedicated return line is not the best setup, but there is no reasonable way to run such a line in my layout. I will replace the crossover valve and see if the ”cold slug” issue goes away.
 
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