Hot water recirc suggestions- Replacing all plumbing

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OnlyinCali

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We are renovating the house and redoing all of the plumbing. The city water pressure is 40psi at the meter(3/4" from meter to house) , which city says is acceptable. We used to have 1/2 copper throughout house but we are going to upsize all of the main lines to 3/4" copper and use 1/2" from the main runs to each sink/shower/etc. Hopefully this will help make showers more enjoyable as water output was crappy before.

The main question I have is regarding recirculating the how water. From what I read, there is a strong chance that we will have a significant hot water delay now that most of the lines will be 3/4". We plan on upgrading to tankless water heater in the future, but not for another couple years. Which recirc setup would you guys suggest? Would it be best to run a return line from the furthest sink or are the newer under-sink setups sufficient? I just want to "do it right" the first time and be done with it. What is the "right" way in this situation? IF I do indeed need to run a recirc line from furthest sink to hot water heater, is it safe to assume this can be 1/2" even though the feeds will be 3/4"?

Suggestions?
 

Terry

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You normally run a 1/2" back to the water heater on a recirc line. That gets a check valve, and a pump. You can run the recirc all the time, or add a timer to it, or/and an AquaStat to turn the pump on and off, maintaining a warm return line.
Some tankless come with a recirc built in. That would be my choice, there is a lot less plumbing to do that way.
Typically I only run two plumbing fixtures on 1/2", so a lav and a tub could be run from the same 1/2" line. For two bathrooms, I'm looking at either a 3/4" line, or two 1/2" lines. The cold gets a 3/4" for a bathroom as the toilet kicks it up a bit and flushing the toilet while in a shower does make a difference.
 

OnlyinCali

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fantastic, thanks for the reply. When you say some tankless have a recirc built in.... Does that mean I don't need to run a 1/2" return at all or does that simply mean I will have a place to connect it to if I run the line? Excuse my ignorance. I just want to make sure I run everything now so I don't have to open walls later to add a recirc line.

edit- Is there any benefit of running the recirc line over the under counter self contained setups? They seem like a patch but I don't know anything about them.
 
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Terry

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The built in recirc units still need the 1/2" line back, but the pump and the reserve tank is built in. A tankless needs a reserve tank for the return line.

The undercounter crossover uses the cold line as the return. That means that when you drink from the cold side, you're drinking from the water heater tank. God knows what's brewing in that tank.
 

Reach4

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From what I read, there is a strong chance that we will have a significant hot water delay now that most of the lines will be 3/4". We plan on upgrading to tankless water heater in the future, but not for another couple years.
If you are planning to switch to tankless in the future, make sure you run the gas pipe or electric system that can support that.

Tankless seems like a good idea, but if you continue reading during those couple years, you may find them to be failure prone and temperamental.

Another thing to consider is to use at least some PEX pipe. If you home run the hot lines to the lavatories with 3/8, they will give hot water much quicker than 3/4 or even 1/2 inch copper would . If you could run your hot with a manifold system and keep a branch system for cold, you could have the best of both.

Recirc does save water, because you will discard some water waiting for hot with even 3/8 PEX. Recirc takes more energy. That energy is to produce the hot water, run the pumps, and to overcome the heat radiated from the hot pipes with AC. One way to run recirc is to recirc slowly all of the time. Second most efficient is to recirc slowly on a timer. Most energy efficient recirc would be to have some control turn on a higher rate recirc using a control -- be that a button or motion sensor. A minute or so after pressing the button or being motion detected, the hot water arrives.
 

Jadnashua

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When you take into account the cost of the water, sewer, heating water...a properly setup recirculation system that runs on a timer during the high use times of the day actually SAVES energy, especially if you have to pump your own water from a well. You do need to insulate your water lines to achieve this, though.

I have a RedyTemp unit and I find that if I set the temperature so I get warm water at that sink, everything behind it is almost instant hot. And, if I flush the toilet, that purges essentially all of the warm water out of the line. I have an indirect, and it stays pretty hot, is a SS tank, so I'm not particularly worried about there being anything growing in the tank. The system is now about 12-years old, runs on a timer, and works as well as the day I installed it. FWIW, it works just fine if you use a dedicated return line verses the cold line, too.
 
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