3/8" Pex pressure loss

[sgt_a_bomb]

I am going to be running a Viega homerun system using a combination of 3/8" and 1/2" lines. 3/8" for sinks, toilets, etc.

My question is... how far can I run the 3/8" lines without having too much pressure loss? I am prepared to study the charts and calculate this more carefully myself, but I thought I'd ask if there is a general "standard" answer that will possibly be good enough. How far can you run 3/8" before you have to start being worried?

I am running off a well and can adjust my pressure in. On the longer runs (possibly up to 30 feet of tubing) will only rise about 2 feet from the manifold to the level of the fixtures).

Thank you for any input.

 

[Matt30]

Why bother running 3/8" at all? 1/2" feeding fixtures, although not code, is pretty much standard practice world wide. Why do something so uncommon? You're killing your pressure right off the bat.

 

[sgt_a_bomb]

From what I can tell, it is not necessary for a homerun system where there will not be fittings in the way restricting flow. I've researched it a lot, and I cannot find evidence showing me I should settle for the 2X wait time for hot water, for 1/2" compared to 3/8". It is not all that uncommon really to use 3/8", if you look at online forums, or call Viega directly. Their tech's clearly have their heads screwed on straight, they have no motivation to sell us on 3/8" (costs less), and they will explain to you that 1/2" simply isn't necessary for low-flow fixtures. So why use 1/2" and wait twice as long for hot water?

I'm interested in anyone with information supporting or opposing what I'm saying above. I'd say I'm about 80% or 90% convinced to use low-flow fixtures with 3/8" lines. I just cannot tell at this point, why I wouldn't do it.

 

[havasu]

I have never seen 3/8" used.

 

[frodo]

""""""I thought I'd ask if there is a general "standard" answer that will possibly be good enough. How far can you run 3/8" before you have to start being worried? """""'

Standard answer, or rule of thumb, also "the code" 1/2'' is minimum ID pipe size



what size pipe do you plan to run to the manifold to feed it?

 

[plbgbiz]

...I just cannot tell at this point, why I wouldn't do it.

Because unlike some forum posters and tech support at the manufacturer, an experienced licensed Plumber (Frodo) that actually answers to his customers for what he does, said not to. It is not wise to always install everything according to manufacturer's "minimum" standards.

Stop searching for what you want and accept what you need.

-OR-

Run 3/8" and live with a substandard system.

 

[frodo]

it is not pressure that will be lacking. 50 psi at the meter is 50 psi. its a constant

what will be effected is volume.

as in, dear forum, why i aint got no water in my shower. it dribbles out like a 70 year old man taking a whiz

our answer, do you have an obstruction in your line

you.....no,,brand new pipe

us. what size

you 3/8

us..change it out
yeah, we are raggin on ya, all fun aside, minimum pipe size is 3/4 into a 2 bath house
minimum pipe size is 1/2'' to the fixtures

in my house, 1'' from the meter to the heater, 3/4 to everything

my shower heads knocks me down....i like it!!!!!!!!!!

 

[havasu]

Yeah, I wonder how long it would take to fill a toilet?

 

[sgt_a_bomb]

Well... you guys are talking me out of it. I don't need to do the minimum, so I guess I wont.

I am intrigued by your comment Frodo, 1" from meter to heater and 3/4" to all fixtures. I do like a shower with plenty of water! I'll never hear the end of it if my wife's new awesome shower doesn't blow her away!
I was planning to run 1/2" to tubs and outdoor faucets. You used 3/4" for everything even the kitchen sink?

I am now leaning toward 1/2" to everything, but your comment has me wondering if I should go 3/4" on tubs/showers and hose bibs.

I will be feeding a total of 4 full bathrooms. One is in a guest house which will not be used much. I'm planning to put a little water heater out there, and run 3/4" to it. The other 3 are all in the main structure and will be USED. I'm probably going to go with a constant hot water tank for the house.

When it comes to pipe selection and crimp VS cinch VS other systems... any advice?

I've spoken with Viega and from what I can see online, this is probably the system for me. however, I am open to advice on this subject. I was planning to use fostapex for any 1/2" or 3/4".

Thanks all!

 

[frodo]

4 full bathrooms? if you have 4 bathrooms you NEED 1''

instead of guessing

4 toilets ----------- 2.5 --- 10
4 tub and showers-- 4 ---- 16
2 shower's -------- 2 ---- 4
6 lavatories--------- 1 ---- 6
1 washer ----------- 4 ---- 4
3 hose bibs---------- 2.5 ---- 7.5
1 kitchen sink ------ 1.5 ---- 1.5
1 dishwasher ------- 1.5 ----- 1.5
----------------------------------30.5 total fu's

sprinkler system ??/ --1 unit per head......... did i for get anything?

if your meter is 100' or closer to your house you need 1" service over 100' you need 1 1/4"
this is based on no sprinkler system

 

[sgt_a_bomb]

Yes 4 full bathrooms, but one is tucked back in the "bunk house" and will receive little use.

I will need to check, I am right on the edge around 100 feet from the well to the house. No harm in using 1.25" to be on the safe side, correct? I think there is 1/5" PVC in the ground currently which I plan to replace with PEX.

What is your PEX of choice? Do you use propex or another system? Any suggestions?

 

[frodo]

I do not use pex, I use copper for yard piping [meter to house] i would use sch 40 pvc

with 4 bathrooms 1 would use 1 1/4 to the house.

how many water heaters?

 

[sgt_a_bomb]

One water heater in the house, one in the "bunkhouse".

What PEX do you use for indoors?

 

[frodo]

one 40 gallon for 3 bathrooms? kinda pushing it aint you?

i do not think you will be happy with that. can you split the house up?

2 baths on 1 w/h maybe the washing machine

master bath and kitchen on the other?

I try not to use pex if at al possible, i use copper.

if i do use it, blue/red wirsbo

do you have a floor plan you can scan /copy to here

 

[sgt_a_bomb]

Thank you for all the help. I'm putting together a drawing for clarity. I should have done this to start off.

 

[frodo]

we like drawings!!!!!!

 

[sgt_a_bomb]

Attached is a drawing, I can add to it if there is anything missing that would be helpful. I appreciate any input you have.

It looks like the first image I attached didn't work, I tried it a different way and it appears to be working but you might need to zoom out to see the whole thing.

thank you for any input!!

 

[frodo]

what is the water in the mud room for?

where is the meter located front , back, l side, r side??ghg

what size meter is installed?

what psi is at meter?

 

[sgt_a_bomb]

Thank you for your reply!

Answers....

what is the water in the mud room for? - I put a drain in the floor, it is a concrete floor, there will be a nozzle to rinse off dogs etc.

where is the meter located front , back, l side, r side??ghg - no meter. Runs off a well. Pressure I will need to confirm. Your drawing showing the line is actually dead accurate, the well is about 75' from the house. Maximum 100ft run to the water heater.

what size meter is installed? - I don't think this applies since I'm running off a well, but please correct me if I'm wrong.

what psi is at meter? - Again, since I'm running off a well, I don't think this applies but let me know if I am wrong.

I also attached some pictures of the tank on the well, in case this is helpful.

 

[sgt_a_bomb]

Your recommendation to use two water heaters in the house is well noted, I will do that. There is a perfect place for the 50 gal, just below the master bath.

However, what about a tank-less system? We are installing propane, and have been considering going with constant hot. Would we still need two?