Hello
I need to run pex supply lines to an apartment above our garage. When the garage and mudroom were attached to the house two years ago, the plumber left two lines running from the house to the garage, one for cold, one for hot. Both are 1/2 “. I would prefer 3/4″, but I’m stuck with 1/2” because the lines run from the house, under a slab where the mudroom is, to the garage.
-will I be fine running these 1/2″ mains and branching them off to each fixture?
-would it do any good to transition the 1/2″ mains to 3/4″ where it enters the garage?
Thank you
Replies
It is not going to do any noticable good to go any larger. But it may be all you need depending on how many fixtures are up there.
Wallyo
Thanks for the response
I assume you mean it won't do any good to transition to 3/4" because the supply water still would have to go through the 1/2" section under the slab before it got to the 3/4"? And therefore the 3/4" line would only be able to supply the amount of water that the 1/2" was giving it? Thats what I figured would be the case.
The total number of fixtures in the apartment, including washing machine and dish washer, would be 6, but I imagine only one fixture will be running at a time usually so I guess I'm ok with one 1/2" feed.
Actually, going from 1/2" to 3/4" for the remainder of the run would make a small difference in the flowrate. I don't have the formula here, so can only generalize from a hazy memory, but the flowrate of water through a pipe is both of function of diameter of the pipe and the length of the pipe, assuming other factors remain constant. Thus a single run of length "L" of pipe of 1/2" would have a lower flowrate than the same length of pipe in which half of it was increased to 3/4". In normal plumbing, the cross section of faucets tend to be less than the cross section of the pipe. However, the restriction to the flow for the short distance through the faucet is much less than it would be if the entire pipe was that diameter. What happens is that the velocity of the flow increases for the distance of the restriction, which increases various losses. When the water gets to the wider pipe, it slows down and the losses per foot decrease. However, in your case, I doubt that it would make a noticeable difference unless the run under the slab was quite short in relation to the total run.
Exactly, I did say noticable difference. Don't know if your well or city h2o but what is it from the final source.Not that it is earth shattering but there is a bit of extra cost with the3/4 yes at some point you would reduce it down to 1/2, but need to weigh that in to.Wallyo
With a setup like this you cn gain significant advantage by putting an expansion tank on the lines before branching out i the outbuilding.
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"You cannot work hard enough to make up for a sloppy estimate."
So the expansion tank goes on the garage/apartment side of the 1/2" lines and can supply 3/4" lines? That would be something to consider. How complicated and expensive does that get. On a related note, could I use the same thing to supply an outdoor irrigation setup that our house could'nt handle?
Thanks
You'll need two tanks, one for hot and one for cold or better to have one for cold only and feed to a small water heater on a switch that ccould be turned on only a needed. It will improve the pressure and flow rate but only enough for domestic usage. It won't work for an irrigation system because it doesn't improve the long term throughput of the 1/2" pipe, though if you did have a small water heater at the out building you could supply it with cold water from BOTH half inch lines to the expansion tank and the bigger size 40 gallon tank would be better than the smaller ones. And yes you could run 3/4 between the expansion tank and the bathroom but probably not much difference in throughput.------------------
"You cannot work hard enough to make up for a sloppy estimate."