Hot Water Recirc. w/ dedicated return

[ellamas]

Hello,

Hot water would take over two mins to come out of kitchen and master bath faucet. I knew I had a couple options for installing a recirc. system. I considered installing a pump at the HW discharge with under sink T valves, but ultimately decided against since I was adamant on not having hot water push into my cold water line. I realized it would be very minimal but I'm a bit particular about the way I want things. Due to my hard requirements, at times I am faced with having to do additional work to get it "just right." Please see below on where I need some help please.

I decided to go with installing a dedicated return line from the furthest (or what i thought) fixture, and pump the water into the cold water side of the water heater. I did research on this and installed all the proper valves and fittings. Please referencing the attached pics. I chose the master bath as the furthest fixture and ran a 1/2" soft copper L line to the pump in the garage, which again pumps into the cold water side. I installed check valves and the master bath has instant hot water - works perfectly!

The bad news is the kitchen sink saw minimal to no improvement. My home is a slab foundation therefore didn't know exactly how the plumbing lines ran. Probably could have had a plumber trace the lines with a fancy tool, but I of course didn't do that, so here I am.

My thoughts now is to run a second return line from the kitchen sink and Tee at the inlet of the pump. Pls see pics. Running the line will not be so fun but know it can be done. My main concern is doing all this work and system still doesn't function as expected. Did some research but unsure if I could simply tee both return lines at the pump inlet or if I need to install some flow control valves, so that I can modulate the flow of each return line. My concern is if I simply tee what if more water will flow from master bath return line vs kitchen return line, or vice versa. At this point, I really need to be 99.9% sure that this will work as I'm sure everyone can appreciate that running the return line to the kitchen sink (with window above) will take some effort. If I can simply tee without any additional valves then all the better

Did talk to a plumber and he at first said to install the T valve under the kitchen sink, but I don't see how that would work since in my application the pump is pumping into the WH vs. for a pump system with T valves the pump is installed on the hot water discharge.

I appreciate any help and recommendations.

Thank you.

 

[CountryBumkin]

The problem is that your kitchen is on a different branch of the hot water circuit. So you are recirculating the water in the hot line from the bathroom but nothing is moving in the hot line to the kitchen.
If you put the Comfort Valve (T fitting or whatever valve came with your kit) under the kitchen sink, it should work because your re-circulation pump is increasing the pressure on the hot side lines, so that additional pressure will allow the higher pressure hot water to move into the cold water line under the sink (as long as the thermostatic T-fitting valve allows it to be open).

 

[Sponsor]

 

[ellamas]

If you put the Comfort Valve (T fitting or whatever valve came with your kit) under the kitchen sink, it should work because your re-circulation pump is increasing the pressure on the hot side lines, so that additional pressure will allow the higher pressure hot water to move into the cold water line under the sink (as long as the thermostatic T-fitting valve allows it to be open).

Thanks for the reply.

I think I see your point and T valve could work despite having the pump on the cold inlet of the WH vs. discharge. Can other plumbers please confirm?

Also, I didn't buy a kit as its a pump with a dedicated return line. Of course, I could buy one of those T valves since they are relatively inexpensive. My concern about pushing some warm water to the cold still remains, though. Especially since i'm going to have an RO under sink system installed and i don't want to drink water coming from the WH.

 

[CountryBumkin]

I don't know how/if it work on the return side. The instructions say to mount it on the hot water line at the water heater (pump is pushing hot water). I'm not sure if it will work the same on the cold water return side of the recirculation pipe where its pulling the water. We will both need to wait for a real plumber to reply. Good luck.
http://us.grundfos.com/content/dam/GPU/Literature/COMFORT/LUPTL043-1005-ComfortSystem-I&O.pdf

 

[Reach4]

My thoughts now is to run a second return line from the kitchen sink and Tee at the inlet of the pump. Pls see pics. Running the line will not be so fun but know it can be done. My main concern is doing all this work and system still doesn't function as expected. Did some research but unsure if I could simply tee both return lines at the pump inlet or if I need to install some flow control valves, so that I can modulate the flow of each return line. My concern is if I simply tee what if more water will flow from master bath return line vs kitchen return line, or vice versa.

That modulating valve in the highest flow return leg makes sense to me. I might just put a valve into the new return line, and only add a valve to the old line if it proved necessary.

My comments are not based on experience.

 

[Jadnashua]

The water will flow in the path of least resistance. If you install a throttling valve in each return line, you can balance them so that they both get flow required to get the source hot. The resistance is a combination of the elevation changes, actual length, the pipe diameter, and the number of fittings and changes of direction. While your soft copper may be one piece, the hot lines to the devices are not and have fittings.

 

[rjbphd]

Hot water return line is to be connected to the drain valve connection.

 

[Jadnashua]

Hot water return line is to be connected to the drain valve connection.

If you have a tempering valve, that can lead to issues. Since there's no cold water coming in, some tempering valves don't mix any cold into the output when you are only recirculating, and the outlet can become as hot as the tank, essentially, bypassing the tempering valve's functionality. This is why some tempering valves now have a recirc input to them...that cooler water gets mixed into the outlet and keeps things from getting too hot. If you think of it this way, since there's no new water coming into the hot water system and tank, there's no flow from the cold side, so you can't add cold water to the tank's outlet, so it cannot temper the water. Having a recirc input, keeps things working.

Dumping it into the drain valve will work when there's no tempering valve, but won't work with all that do have a tempering valve.

 

[ellamas]

The water will flow in the path of least resistance. If you install a throttling valve in each return line, you can balance them so that they both get flow required to get the source hot. The resistance is a combination of the elevation changes, actual length, the pipe diameter, and the number of fittings and changes of direction. While your soft copper may be one piece, the hot lines to the devices are not and have fittings.

Thank you. This is what I was thinking. By chance do you have a throttling valve model that you'd recommend? Is this the same as a flow control valve? Some of those are expensive and just need in 1/2" size. This project is already costing more than I budgeted. Could have gone with the comfort series pump w T valve for a couple hundred, but due to my rigid requirement I'm already in $550+ and that's with cheap labor via my friend helping. Cost of second line not included.

 

[Jadnashua]

Since the flow rate is fairly low, I'm not sure it matters, but this is a question best left for one of the pros...some valves work better at actually adjusting the flow than others. since you application isn't super critical, precise control isn't a huge concern.

 

[hj]

A recirculation loop is like a "race track" the water goes from the pump and returns TO the pump by the shortest route. A "comfort bypass valve" will NOT work since your pump does NOT create a pressure in the cold line which would allow it to work. A pump on the hot water discharge side, WOULD pressuize both the cold and recirculation lines thru a bypass valve.

 

[ellamas]

A recirculation loop is like a "race track" the water goes from the pump and returns TO the pump by the shortest route. A "comfort bypass valve" will NOT work since your pump does NOT create a pressure in the cold line which would allow it to work. A pump on the hot water discharge side, WOULD pressuize both the cold and recirculation lines thru a bypass valve.

Appreciate the response, and understand that. I'm trying to avoid installing two pumps. My question, in short, is how to balance two return lines connected to one pump, plumbed to cold water inlet.

 

[Jadnashua]

If it's installed, and you find that one branch is not getting warm, you need to create more 'friction' in the other by installing a valve to balance the flow between them. I think that almost any valve would work...start closing it off until you find your balance point. A ball valve may be your best bet as a gate valve generally should be fully open or closed, and a stop valve generally has too much restriction even when fully opened. A ball valve can go from fully opened to fully closed, but it's not perfectly linear.

 

[ellamas]

If it's installed, and you find that one branch is not getting warm, you need to create more 'friction' in the other by installing a valve to balance the flow between them. I think that almost any valve would work...start closing it off until you find your balance point. A ball valve may be your best bet as a gate valve generally should be fully open or closed, and a stop valve generally has too much restriction even when fully opened. A ball valve can go from fully opened to fully closed, but it's not perfectly linear.

Thanks would I need a valve in each branch or just the shortest one? Actually, since the branches are of similar lengths and I'm not sure how the supply is exactly plumbed, might be best to install a valve on each branch?

Also, thought ball valves were not ideal for flow control and best for fully open or closed? Of course if ball valves would work in my application that would be great, since they aren't very expensive ~$13 ea.

 

[Jadnashua]

If it's already installed, and one side is not getting warm, put a valve in the other side. Otherwise, it won't hurt to put one on each side. While a ball-valve isn't great at volume control, it will work. Neither a gate valve nor a multi-turn shutoff with a washer are great in your situation since a gate valve will erode if not fully opened or closed, and the typical shutoff has a lot of internal restriction in it and the rubber washer won't last as long in hot water.