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Old 01-03-2016, 10:08 PM   #1
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Using PEX and a loop system for hot, one red only


Has anyone out there piped a house with PEX and used a system whereby they maintain a high hot water pressure and use ONE line only for hot, say 3/4" throughout the whole house??? Has anyone used a 2-3 fitting Tee or manifold-mini sized, for each bathroom, there are 4, and then finish in the kitchen, which is the farthest from the supply line and water heater. Then use a small circulation pump to dump a little into the cold lines - blue. I will put this on a timer. For the cold, has anyone also done about the same thing??? I can do a regular manifold with a lot of home runs, this is a 3500 sf two story house, new construction, 4 baths, 1 kitchen. Looking for a way to maintain water pressure and hot water. Thanks for any ideas. Seems like a bunch of home runs is not too smart??? I could do a branch and trunk line to each bathroom, but I want to try a loop system to keep the hot hot. Any thoughts, experiences out there on this???
Next question, for the bathrooms with shower and tubs what size lines do you run??? House has great pressure from the street, 120 psi estimated, before pressure regulator. Will do a auto sprinkler system also, backflow required, expect to come in with a 2" line, split in a Y, one line for autosprinklers at 1", have 1" diameter line for house, so can go bigger as needed in house(bigger than 1/2" or 3/4") to get the good pressure I am looking for, thanks.

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Old 01-04-2016, 10:31 PM   #2
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Has anyone out there piped a house with PEX and used a system whereby they maintain a high hot water pressure and use ONE line only for hot, say 3/4" throughout the whole house??? Has anyone used a 2-3 fitting Tee or manifold-mini sized, for each bathroom, there are 4, and then finish in the kitchen, which is the farthest from the supply line and water heater. Then use a small circulation pump to dump a little into the cold lines - blue. I will put this on a timer. For the cold, has anyone also done about the same thing??? I can do a regular manifold with a lot of home runs, this is a 3500 sf two story house, new construction, 4 baths, 1 kitchen. Looking for a way to maintain water pressure and hot water. Thanks for any ideas. Seems like a bunch of home runs is not too smart??? I could do a branch and trunk line to each bathroom, but I want to try a loop system to keep the hot hot. Any thoughts, experiences out there on this???
Next question, for the bathrooms with shower and tubs what size lines do you run??? House has great pressure from the street, 120 psi estimated, before pressure regulator. Will do a auto sprinkler system also, backflow required, expect to come in with a 2" line, split in a Y, one line for autosprinklers at 1", have 1" diameter line for house, so can go bigger as needed in house(bigger than 1/2" or 3/4") to get the good pressure I am looking for, thanks.
I'm right in the middle of repiping my 60s house with pex. I am adding a dedicated hot water return line in 3/4". So the hot water starts at the water heater travels in a big loop and will return to the water heater where it will enter the bottom of the WH through the drainage bib by way of an added T fitting. I am going with a ACT D'MAND pump with a button that will prime the hot water when I need it. Not a fan of timers or transferring hot water to the cold side. I am using a modified manifold set-up with small manifolds that feed groups of fixtures. The drops are 1/2" to each fixture. I'm using 3/4" mains. Good luck.

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Old 01-04-2016, 10:53 PM   #3
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TW - thanks much for the reply. I may be going with a loop, too. Was shown how to run a one way and then into the cold originally, told you save by not heating the loop from the farthest fixture back to the water heater, but it does not make sense? I can't decide what is best? I know I will start at the water heater and probably just run a 3/4" supply over each bathroom and then keep my runs short, 1/2" to the fixtures and keep going to the kitchen, the farthest use from the water heater, then REDUCE to 1/2" and loop back to the water heater, forget the pump and going into the cold. I guess just the energy to heat that last loop from the farthest fixture homerun back to the WH is wasted using your way? Who wants an extra pump under a sink anyway, best out on the WH. p.s. did you check with the manufacturer on the hookup of the return into the hose bibb? is it ok to do that? I would like to know, get a model that allows that. See if they say somehow it can void a warranty or something, just saying...better safe than sorry. I have heard of worse.
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Old 01-04-2016, 11:19 PM   #4
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TW - thanks much for the reply. I may be going with a loop, too. Was shown how to run a one way and then into the cold originally, told you save by not heating the loop from the farthest fixture back to the water heater, but it does not make sense? I can't decide what is best? I know I will start at the water heater and probably just run a 3/4" supply over each bathroom and then keep my runs short, 1/2" to the fixtures and keep going to the kitchen, the farthest use from the water heater, then REDUCE to 1/2" and loop back to the water heater, forget the pump and going into the cold. I guess just the energy to heat that last loop from the farthest fixture homerun back to the WH is wasted using your way? Who wants an extra pump under a sink anyway, best out on the WH. p.s. did you check with the manufacturer on the hookup of the return into the hose bibb? is it ok to do that? I would like to know, get a model that allows that. See if they say somehow it can void a warranty or something, just saying...better safe than sorry. I have heard of worse.
The savings is not in heating but in water. If you pump warm water to the cold line then you will waste the warm water to get the cold water cold again. Also those under the sink valves only seem to last a few years before you have to replace them. You want to keep the return line 3/4". The return is usually Teed to the bib, ACT even shows it plumbed this way in the instructions. Most pump manufactures sell pumps with the under the sink stuff and plain for the dedicated return lines. Also need to insulate at least the hot water lines. I'm in the South and will insulate my cold line as well to help with condensation.
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Old 01-05-2016, 06:30 PM   #5
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Quote:
Originally Posted by Vincent1 View Post
Has anyone out there piped a house with PEX and used a system whereby they maintain a high hot water pressure and use ONE line only for hot, say 3/4" throughout the whole house??? Has anyone used a 2-3 fitting Tee or manifold-mini sized, for each bathroom, there are 4, and then finish in the kitchen, which is the farthest from the supply line and water heater. Then use a small circulation pump to dump a little into the cold lines - blue. I will put this on a timer. For the cold, has anyone also done about the same thing??? I can do a regular manifold with a lot of home runs, this is a 3500 sf two story house, new construction, 4 baths, 1 kitchen. Looking for a way to maintain water pressure and hot water. Thanks for any ideas. Seems like a bunch of home runs is not too smart??? I could do a branch and trunk line to each bathroom, but I want to try a loop system to keep the hot hot. Any thoughts, experiences out there on this???
Next question, for the bathrooms with shower and tubs what size lines do you run??? House has great pressure from the street, 120 psi estimated, before pressure regulator. Will do a auto sprinkler system also, backflow required, expect to come in with a 2" line, split in a Y, one line for autosprinklers at 1", have 1" diameter line for house, so can go bigger as needed in house(bigger than 1/2" or 3/4") to get the good pressure I am looking for, thanks.
Some houses are piped with recirc lines. The normal method for new work is run the 1/2" HW loop back to the water heater from the furthest fixture. The pump is installed there instead of under a counter.

You can run the Hw line out to the bathrms and use tees or manifolds to serve the bathrm fixtures- the sorter the branch lines the better the performance.

To size the system properly, you need to know your water pressure on the house side of the PRV and the water fixture unit rating of each fixture.
Then you can reference water pipe sizing charts available on-line.
By using these sizing charts, you can optimize your flow rate
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Old 01-05-2016, 09:16 PM   #6
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Not sure about other pump manufacturers, but ACT recommended 3/4" return.

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