Looking to upgrade 50 yr old 1/2” trunk+branch plumbing

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jadnashua

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A shutoff on PEX just seems too flexible to me...I prefer to transition to copper. If you do connect to PEX, a standard compression valve works just fine if you use the internal stiffener...the valves are identical. You can buy the stiffeners separately, or packaged with the valves. With a Sharkbite shutoff, you have the potential for it to turn on the tubing as well as flex the tubing. The SS grippers can gouge the PEX if the valve gets a little stiff when you're turning it. If you're not careful taking it off, when it comes time to replace it, you may have damaged the PEX, making a seal difficult or impossible without enough slack to cut it off so you have fresh tubing to attach to.
 

Jeff H Young

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A shutoff on PEX just seems too flexible to me...I prefer to transition to copper. If you do connect to PEX, a standard compression valve works just fine if you use the internal stiffener...the valves are identical. You can buy the stiffeners separately, or packaged with the valves. With a SHarkbite shutoff, you have the potential for it to turn on the tubing as well as flex the tubing. The SS grippers can gouge the PEX if the valve gets a little stiff when you're turning it. If you're not careful taking it off, when it comes time to replace it, you may have damaged the PEX, making a seal difficult or impossible without enough slack to cut it off so you have fresh tubing to attach to.

something negative about every way you do it having an extra joint inside the wall is another chance for damage as well. My house which I didn't build is 22 years old with PEX and and standard compression stops with the stiffener inside the tubing its worked fine yea the stubouts are a little bendy we all know that you have to hold valve and turn handle (or you should) . My opinion is spend the extra money and repipe entire home with copper type L. but no one wants to spend the money or they think PEX is better in which case fine then run PEX but leave your copper where its exposed rather than put additional joints in the wall, just one way looking at it . under a cabinet id leave my stub a little long on my own house someone else's I might want it a little closer for cosmetic reasons only.
 

yNotry

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Thanks Jeff, JADNashua, Reach4 and Wayne,

I appreciate and have incorporated all your feedback. I’ve decided to go with pex crimp to compression stop valves where the pex is held by drop ear bend supports attached to studs since a) the plumbing is 50+ years and comes up thru floor and b) already bought the supplies.

Been working through design + remaining supplies needed. Have some questions:

1) For supply to larger 45 gal soak tub, am thinking of running 3/4” pex for hot and assume the same for cold. Will running the 3/4” pex out of 1/2” port of 1” manifold greatly reduce the flow?
2) For RO tee, would it be worthwhile to run off 1” bypass rather than 1” supplying cold manifold?
3) Have been asked to install tub spout on side of soak tub for double the enjoyment! Any issues to be concerned about other than someone banging on spout while showering? Reading up the length seems to be within allowed limit. And I’m figuring 3/4” tub drop will allow for even longer.
4) Have read up some and have questions on recirc which I will ask separately.
 

yNotry

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FWIW, most engineered recirculation systems do not run the pump until you have full hot at the sensing point. Yes, you may need to do that in a commercial building, like a motel, etc., but generally, the ones I've looked at for a home, do not. The one I currently have is not adjustable, and it shuts the circulation off when the sensing point gets to 96-degrees, and doesn't turn it back on again until it drops to like 88 or so...I may be off a degree or two on it, but it's in that ballpark...this is to minimize the heat energy losses, but gives you instant warm, and hot many places. In my situation, my upstairs vanity is the furthest from the WH, while the tub/shower is closer. When the timer enables it to run, I'll have warm at the sink instantly, but because the shower is closer, it gets hot quicker. It's only got a very small motor (like 9W), and runs maybe 45=seconds about every 15-minutes or so, depending on the season.

I've seen some run the recirculation until 105-degrees, and my original one that died after nearly 20-years (the check valve died, not the pump, but the company had gone out of business just the year before so I couldn't get the proprietary part, and I didn't feel like modifying things) was adjustable, while the new one is not (although they do make a model that is).

Without the pump (if I happen to get up early before the timer turns it on), it can take like 90-seconds to get hot water upstairs...I much prefer the recirculation! What you do NOT want to do, is over pump it...high velocity, hot water flow can literally erode the pipe from the insides, plus, the pump costs more as does the electricity to run it. Pex has a maximum recommended flow velocity (it's higher than copper's), but on copper, with hot water, it's a maximum of 5fps. With the ID of copper, that's only 4gpm on a 1/2" pipe, and 8gpm with a 3/4". You'd have to check the pex manufacturer's design guidelines for velocity. Keep in mind that higher velocity also means more dynamic friction, and thus, more dynamic pressure drop.

You may find that hot water recirculation systems eventually become mandatory to help save water. They certainly do that, but if combined with a timer or manual activation, can also save power. Even with your own well, every gallon you pump out of the ground, you're paying for the electricity to pump it.

They can not save energy as far as heating water. The best you can do is use manual activation to avoid an increase in water heating requirements.

Cheers, Wayne

Edit: OK, that's a little too absolutist. If you can arrange for the recirc to not cause the water in the hot water pipes to be hotter/longer than if you don't have it (e.g. a manual activation system that just pumps the water back into the cold line), so it just does the equivalent of running the hot water to the temperature at which you want to use it, then it avoids increasing the heat load on the water heater.

And then if you also direct that tempered water (at least as warm as indoor air temperature, which is presumably warmer than your incoming cold water) back to your hot water tank, then you do save a little bit of heating required for your hot water. That will be a small effect.

So I need to revise my statement to saying that recirculation almost never saves heating energy.

Don't see a dedicated line to the recirc system as being a energy waster just gotta have it set up correctly, I'd rather have the return line and be able to adjust it in many different ways a timer , thermostat, or remote. You can set it up the same if you want as one that doesn't have a return , advantage being that if you decide you want a good system you don't need to add a return line later tearing out drywall etc. a 1/2 piece of PEX is real cheap to run now not so much later

Thanks JADNashua, Wayne and Jeff for the suggestions. Given what you’ve said, what I’ve read and that I will have a 6 branch manifold, I’m thinking the following:

a) Separate 1/2” recirc lines to furthest fixture in each group (5 or 6 depending if include washer) running back to..
b) Separate 1/2” manifold with 5-6 branches running to..
c) Recirc pump with thermostat, check valve, and timer running into HW heater cold supply..
d) Check valve and 1/2” tee outside of wall into 1/2” pex hot supply right before hot stop valve.

I have the following questions:
1) Any issue if I make recirc lines all same length by adding loop(s) for shorter lines (20,22,17,11,25,21 ft) vs buying more expensive balance adjust? Will add a total volume less than 1/4 gallon.
2) Any reason to get bigger than 1/2” manifold or smallest available? I’m assuming I want to minimize total volume of recirc.
3) Am trying to find low flow (2 gpm?) recirc pump with built in thermostat. Found B&G EcoCirc 4 gpm https://www.supplyhouse.com/Bell-Go...-Plug-Lead-Free-Brass-1-2-FPT#reviews-content Any other pumps you’d suggest with lower 2 gpm+thermostat? Any reason to get integrated check valve or timer when they can be bought and replaced separately if/when they go?
4) Any suggestions for check valves? I’m finding $15-20 each which seems high.
5) Am I missing anything? Am I understanding and laying the recirc out correctly for my situation?
 

yNotry

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Reverse Osmosis? Lines to RO units are low flow.
Yes, understood. Was asking since PEX tee fitting restricts/reduces flow some. Was thinking less restriction in main cold line to manifold is better, especially for adding just a low flow RO.
 

wwhitney

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In re recirc, the first thing you need is a dimensioned floor plan showing the location of the water heater, where you can put the manifold, and where each hot supply needs to be. I would think a recirc system would be more efficiently laid out as a single trunk (with a return line) running near each fixture, with short branches off the trunk. While a manifold system without recirc could work well if all the fixtures are located close to the water heater.

Cheers, Wayne
 

jadnashua

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For a short distance, the water will accelerate through the restriction, so pulling off of a 1/2" port from a larger manifold, although it will lower the output, isn't as bad as having the entire line smaller, so your dynamic pressure drop won't be much when feeding into a larger line. When the restriction is long enough, then the friction becomes much more of an issue. Ideally, would have a manifold with different sized outlets, or, maybe a T on the inlet to your high volume line to the tub instead of the manifold port. You could put a shutoff valve in that line if you wanted to isolate it.
 

John Gayewski

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I kind of skimmed this thread not reading the whole thing there's once thing that stuck out. 3/8" outlet piping isn't allowed. 1/2" is the minimum UPC allows.
 
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