PEX re-pipe question.

[Piperca]

I experienced a recent slab leak. I need to re-pipe and was considering PEX pipe. My house is approximately 1500 square feet. The plumbing chase is in the center of the house, which services two bathrooms (back to back) on one side of the chase and the kitchen on the other. It would require approximately 50' of pipe (routed) to reach the plumbing chase from the water heater in the garage.

After researching the different methods (home run v trunk and branch), I have a question. Is it acceptable to run "trunk and branch" on the cold side and "home run" on the hot? It makes sense to me that the only benefit, for my situation with the home run method, is shorter wait times for hot water; am I missing something? Obviously, I'm trying to reduce the amount of PEX lines I need to run.

Any assistance would be greatly appreciated.

 

[CountryBumkin]

The benefit of the "Home Run" layout is that you start at a manifold where you then have individual shutoff valves for each Run so you can shutoff any run to make repairs or such, without having to shutoff all the homes water (like with a Trunk layout). But if there is no water flowing through the lines (say at night while your sleeping) those lines are going to cool down so in the morning when you turn on the faucet you will still need to wait for the hot water. A "Home Run" layout may shorten the path the hot water needs to take to get your bathroom (and quicken the time it takes to get hot water), but not by much. IMO
A benefit of the Home Run layout is that if you have a lot of demand (many faucets open, filling tub, running washer, etc.) at the same time you would have more flow available since each faucet (kitchen, bath, wash room) have their own feed lines, whereas feeding off a single "Trunk" line you may have a reduced flow (because there is too much demand for the single line to supply).

If you really want to improve on the hot water wait time, run a second line from that bathroom back to water heater for a "return" line so you can setup a recirculation loop.

 

[Sponsor]

 

[Piperca]

Thank you for your input, it now makes sense.

So, I'm assuming, the recirculation line should run from the end of the trunked 3/4 line, correct? What pump setup would you recommend and is there any tips/tricks that would help in making it run most efficiently?

 

[CountryBumkin]

You can use a Trunk and Branch layout "just for the bathroom" where it only supplies the faucet, shower, and tub (other the areas of the house could be on a different Trunk and Branch layout using a different feed without a recirculation line). So the hot water line runs directly to the bathroom and then returns to the hot water tank via the return line. Or you could have everything in the house that uses hot water on the same Trunk line (like in the link below) with the last (furthest fixture) having the recirculation line on it.

See this article: http://www.finehomebuilding.com/2013/03/07/hot-water-circulation-loops
I have a GruFundos Comfort recirculator which is the old style and turns on and off by programming the timer on it (you would set it run from like 5am to 6am and 9am to 10am or such depending on your families schedule). There are models that use a "presence senor" so when you walk into the bathroom the pump turn on, there are also models that use a button you would press in the bathroom when you enter to turn on pump. Lastly some designs have no pump, they rely on convection and gravity to move the water.

I'm not a plumber, so there may be a professional opinion on which is better. I just did the master bath with the recirculation setup - and not all of the house.

 

[Piperca]

Great information, thank you!

 

[Jadnashua]

There are lots of recirculation kits out there. One of the things to consider while repiping is to run a separate return line verses the more common, retrofit system that utilizes the cold water line (when you can't easily run a new return line). That will somewhat negate your desire to minimize the use of pex.

On many systems, the pump runs continuously, on some, there's an aquastat that shuts it off. The one I have does that and I find it only runs maybe 45-seconds, 4-5x per hour verses constantly. Now, the pump isn't huge, so the power use is not great, but still, cycling verses constant has some benefits (other than wear - on/off wears things faster than constant running up to a point).