Doesn't Cold Water to Water heater First? Is my plumber wrong?

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franksr27

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Hey Guys quick question. Is it OK to plumb the cold side of fixtures on the way to the water heater?My plumber said its fine to plumb things on the way to the water heater. I always thought you bring it to the water heater first and then run lines together. Doesn't this prevent pressure drop etc?

Second question: is there any advantage/disadvantage to running 3/4 hot off the water heater with 1/2 stubs? or is it ok to just run 1/2 off the heater to all the fixtures? does distances/number of fixtures determine what to use? Does anyone know if there is a guide book that goes over all this? I am using a licensed plumber for this project But i find this stuff really interesting and am trying not to ask my plumber a zillion questions. I do bath and kitchen remodeling so I do get the basic construction concepts but plumbing always leaved me a little stumped.

any explanations or resources greatly appreciated!!
 

Reach4

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#1. I don't think it matters, and I am reasonably sure it is not a rule. Do plan for a softener when running pipes. Don't feed soft water to outside spigots that you will use for watering the lawn or garden.

#2. By breaking up the hot into smaller pipes earlier, there is less water in the pipe to a given fixture. There are premium methods called home-run systems that do this. The main advantage is for hot, altho it is often used for both. For the lavatory (bathroom sink), 3/8 pipe is enough. If you ran 3/8 pex to the lavatory, hot water would get there in 55% of the time taken through 1/2, and 28% of the time it would take to go thru 3/4.

1/2 pex would take 51% of the time that 3/4 would take.

So smaller hot pipe will save energy and maybe water. A hot water recirculation system saves the most water, but it takes the most energy.
 

Michael Young

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Hey Guys quick question. Is it OK to plumb the cold side of fixtures on the way to the water heater?My plumber said its fine to plumb things on the way to the water heater. I always thought you bring it to the water heater first and then run lines together. Doesn't this prevent pressure drop etc?

Second question: is there any advantage/disadvantage to running 3/4 hot off the water heater with 1/2 stubs? or is it ok to just run 1/2 off the heater to all the fixtures? does distances/number of fixtures determine what to use? Does anyone know if there is a guide book that goes over all this? I am using a licensed plumber for this project But i find this stuff really interesting and am trying not to ask my plumber a zillion questions. I do bath and kitchen remodeling so I do get the basic construction concepts but plumbing always leaved me a little stumped.

any explanations or resources greatly appreciated!!

you can catch any fixture you want before or after the water heater. It doesn't matter. Run your gutline for your hot with 3/4"

You can catch only THREE fixtures on a 1/2" water supply. That's why I pull a 3/4" (or 1") gutline for both hot and cold when I do repipes or new construction. Always thing towards the future. If you use a full-diameter gutline, 70 years from now, future plumbers will have adequate water without having to re-do all of it. It also lends itself to upgrades you may choose to do in the not-so-distant future. My opinion = full diameter the entire length of the run is the way to go.
 

Dj2

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Your plumbing system is like a tree - complete with a trunk and branches.
Follow the pipe sizing chart, and you will pass inspection.
 

franksr27

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Thanks Guys I really appreciate it! Terry your chart is great! So I have a 3/4 meter, I spoke with my plumber who said run 1'' pipe after the meter to the house and use 1'' as the main supply to feed all other branches. but then I mentioned this as I was picking up materials for him at Fergueson supply and a plumber overheard nd said no way! I would lose too much pressure doing this. Isn't that what the pressure regulator is for? So my plan is to Run 1'' pex in the house with 1/2'' branches for fixtures. sound about right? any reason to run 3/4"? thanks again much appreciated!
 

jadnashua

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The main reason you lose pressure along a distribution system is from either elevation rises (0.43#/ft), or from friction losses. Smaller pipes have higher friction. STatic pressure would be the same regardless of the pipe size, but dynamic pressure (when water is being used) will drop based on the amount of friction.

If using copper pipe, there is some good information in the Copper Institute handbook, which is free to download. It will tell you the friction/flow losses from various lengths of piping at different diameters, and at different flow rates. One major thing to take from their recommendations is to limit the maximum velocity of the water in the pipes...their guideline is a max of 5fps for hot water, and 8fps for cold. Depending on the size of the pipe on say hot, 1/2" pipe equates to only 4gpm, while 3/4" equals 8gpm. Because of the radius-squared factor, a small increase in diameter means a much larger volume the pipe can carry.

Some tests have calculated that using hot water recirculation, along with a timer to restrict its use to normal need times and insulating the pipe, saves money verses the cost to heat the water, pay for that you throw away while waiting for it, the sewerage costs, and the electricity required to pump it around. It is certainly convenient to have it there without any major delays. They're pretty reliable, too...mine is now pushing 12-years without any maintenance or parts required. I have worn out a couple of timers, but those are not part of the actual recirculation system - bought elsewhere.
 
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