1/2" Vs 3/4" Hot Water Line - Page 2 - Plumbing - Contractor Talk

1/2" Vs 3/4" Hot Water Line

 
Thread Tools Search this Thread Display Modes
Old 02-07-2012, 11:12 AM   #21
Contractor of the Month
 
Inner10's Avatar
 
Trade: Control Systems
Join Date: Mar 2009
Location: Ottawa, ON
Posts: 24,448
Rewards Points: 1,562

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Cole82 View Post
All the shutoffs are in one location and less fittings. Just the supply line connection and the manifold connection. The topic of this thread as well I have always been told that 1/2" line gets hot water faster that a main run with branches. Pex pipe is cheaper than fitting to connect to main line. Other than that I don't know that's why I asked.

Cole
Yes and no...

I'd be hard pressed to think the savings of not buying 3/4" T's would be more than buying all that extra 1/2 pipe and shut-off valves.

Think about this, you take a dump, then go to wash your hands with hot water, now the trunk is hot, you get hot water right away at the shower instead of draining long 1/2 inch lines for each fixture.
__________________
The Following User Says Thank You to Inner10 For This Useful Post: Leo G
Inner10 is offline  

Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ContractorTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

   

Advertisement

 

Old 02-07-2012, 06:38 PM   #22
Capra aegagrus

 
Tinstaafl's Avatar
 
Trade: Remodeler
Join Date: Jan 2008
Location: Central Pennsylvania
Posts: 22,556
Rewards Points: 38

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Inner10 View Post
Think about this, you take a dump, then go to wash your hands with hot water, now the trunk is hot, you get hot water right away at the shower instead of draining long 1/2 inch lines for each fixture.


I did for a moment. Sounded like you had the commode hooked to the hot water line.
Tinstaafl is offline  
The Following User Says Thank You to Tinstaafl For This Useful Post:
mehtwo (03-03-2012)
Old 02-07-2012, 06:48 PM   #23
Contractor of the Month
 
Inner10's Avatar
 
Trade: Control Systems
Join Date: Mar 2009
Location: Ottawa, ON
Posts: 24,448
Rewards Points: 1,562

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
I did for a moment. Sounded like you had the commode hooked to the hot water line.
I'm not that rich!

...But I do wash my hands with warm water.
__________________
The Following User Says Thank You to Inner10 For This Useful Post: Leo G
Inner10 is offline  
   
 
Old 02-07-2012, 07:08 PM   #24
Working
 
Cole82's Avatar
 
Trade: GC
Join Date: Nov 2008
Location: Cedar Rapids, IA
Posts: 4,131
Rewards Points: 2,276

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Inner10 View Post
Yes and no...

I'd be hard pressed to think the savings of not buying 3/4" T's would be more than buying all that extra 1/2 pipe and shut-off valves.

Think about this, you take a dump, then go to wash your hands with hot water, now the trunk is hot, you get hot water right away at the shower instead of draining long 1/2 inch lines for each fixture.
There are no extra shut off valves the valves are on the manifold built into it.

You are assuming the trunk/main line is warm but after sitting idle for 10 hours a normal work day. It isn't very warm anymore. Of coarse if you have a stay at home wife she could be doing laundry or dishes through out the day keeping it warm. We will say it's cold now though after the 10 hours. You go to wash your hands after that monster poop you speak of. Now you have to drain that large main line before you get warm water. With the manifold setup it's only a 1/2" line instead of 3/4" or even 1".

Not trying to argue just wondering as the branch setup is unheard of here. I was actually trying to remember the last one I saw on a new house and I think it was 98. I remember back in the late 80's early 90's they were using manifolds in the new development behind our house.

Cole
__________________
The boss of awesome
Cole82 is offline  
Old 02-07-2012, 07:23 PM   #25
Contractor of the Month
 
Inner10's Avatar
 
Trade: Control Systems
Join Date: Mar 2009
Location: Ottawa, ON
Posts: 24,448
Rewards Points: 1,562

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Not trying to argue just wondering as the branch setup is unheard of here. I was actually trying to remember the last one I saw on a new house and I think it was 98. I remember back in the late 80's early 90's they were using manifolds in the new development behind our house.
Must be a regional thing, only time I've ever seen manifolds being used for potable water was when it was a DIY job and the homeowner though it was better for some reason. Never seen a real plumber do it that way.
__________________
The Following User Says Thank You to Inner10 For This Useful Post: Leo G
Inner10 is offline  
The Following User Says Thank You to Inner10 For This Useful Post:
Cole82 (02-07-2012)
Old 02-07-2012, 07:31 PM   #26
Working
 
Cole82's Avatar
 
Trade: GC
Join Date: Nov 2008
Location: Cedar Rapids, IA
Posts: 4,131
Rewards Points: 2,276

Re: 1/2" Vs 3/4" Hot Water Line


Must be a regional thing.

On a side note. If I ran hot water to my toilet would it keep the seat warm?

Cole
__________________
The boss of awesome
Cole82 is offline  
Old 02-07-2012, 11:51 PM   #27
The Grand Wazoo
 
KillerToiletSpider's Avatar
 
Trade: It blowed up real good!
Join Date: May 2007
Location: Illinois
Posts: 3,929
Rewards Points: 1,890

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Cole82 View Post
Must be a regional thing.

On a side note. If I ran hot water to my toilet would it keep the seat warm?

Cole
No, but it will keep the tank from sweating in the summer time.
__________________
I may be going to hell in a bucket, but at least I'm enjoying the ride.
KillerToiletSpider is offline  
Old 02-08-2012, 07:37 AM   #28
Pro
 
TimNJ's Avatar
 
Trade: Remodeler
Join Date: Sep 2005
Posts: 5,509
Rewards Points: 3,414

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Cole82 View Post
Must be a regional thing.

On a side note. If I ran hot water to my toilet would it keep the seat warm?

Cole
When I worked on a military base there was always some plumber who would end up hooking up a toilet to the hot water line.
Gave new meaning to "take a steaming sh**".
The janitors thought it was great. They could sanitize the toilet just by flushing it once or twice.
TimNJ is offline  
Old 02-08-2012, 07:38 AM   #29
Pro
 
TimNJ's Avatar
 
Trade: Remodeler
Join Date: Sep 2005
Posts: 5,509
Rewards Points: 3,414

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Cole82 View Post
Tin this link covers manifold design benefits over traditional systems.

http://www.huduser.org/portal/public...sign_guide.pdf

Flow Rate ft/sec
GPM 3/8” 1/2” 5/8” 3/4” 1” 1 1/4” 1 1/2” 2”
0.2 0.67 0.36 0.25 0.18 0.11 0.07 0.05 0.03
0.3 1.00 0.54 0.37 0.27 0.16 0.11 0.08 0.05
0.4 1.33 0.72 0.50 0.36 0.22 0.15 0.11 0.06
0.5 1.67 0.91 0.62 0.45 0.27 0.18 0.13 0.08
0.6 2.00 1.09 0.74 0.54 0.33 0.22 0.16 0.09
0.7 2.33 1.27 0.87 0.64 0.38 0.26 0.18 0.11
0.8 2.67 1.45 0.99 0.73 0.44 0.29 0.21 0.12
0.9 3.00 1.63 1.12 0.82 0.49 0.33 0.24 0.14
1.0 3.33 1.81 1.24 0.91 0.55 0.37 0.26 0.15
1.1 3.67 1.99 1.36 1.00 0.60 0.40 0.29 0.17
1.2 4.00 2.17 1.49 1.09 0.66 0.44 0.32 0.18
1.3 4.34 2.35 1.61 1.18 0.71 0.48 0.34 0.20
1.4 4.67 2.53 1.74 1.27 0.76 0.51 0.37 0.22
1.5 5.00 2.72 1.86 1.36 0.82 0.55 0.40 0.23
1.6 5.34 2.90 1.98 1.45 0.87 0.59 0.42 0.25
1.7 5.67 3.08 2.11 1.54 0.93 0.62 0.45 0.26
1.8 6.00 3.26 2.23 1.63 0.98 0.66 0.47 0.28
1.9 6.34 3.44 2.36 1.72 1.04 0.70 0.50 0.29
2.0 6.67 3.62 2.48 1.81 1.09 0.73 0.53 0.31
2.5 8.34 4.53 3.10 2.27 1.36 0.92 0.66 0.38
3.0 10.00 5.43 3.72 2.72 1.64 1.10 0.79 0.46
3.5 11.67 6.34 4.34 3.18 1.91 1.28 0.92 0.54
4.0 7.24 4.96 3.63 2.18 1.47 1.05 0.62
4.5 8.15 5.58 4.08 2.46 1.65 1.19 0.69
5.0 9.05 6.20 4.54 2.73 1.84 1.32 0.77
6.0 10.86 7.44 5.44 3.28 2.20 1.58 0.92
7.0 8.68 6.35 3.82 2.57 1.84 1.08
8.0 9.92 7.26 4.37 2.94 2.11 1.23
9.0 11.16 8.17 4.91 3.30 2.37 1.39

Great link there.
TimNJ is offline  
Old 02-08-2012, 07:42 AM   #30
Pro
 
TimNJ's Avatar
 
Trade: Remodeler
Join Date: Sep 2005
Posts: 5,509
Rewards Points: 3,414

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Tinstaafl View Post
Leaving aside the overall volume of flow, at what point is it better in terms of hot water NOW at the faucet to use a 1/2" line to take advantage of the higher velocity of flow? Does that question make any sense?

How is your layout set up.
When I built my place I had my h/w in my mechanical room. After living in the house for a while I ended up relocating it so it was closest to the point of where I actually used most of my h/w. Made a big difference.
TimNJ is offline  
Old 02-08-2012, 07:45 PM   #31
Capra aegagrus

 
Tinstaafl's Avatar
 
Trade: Remodeler
Join Date: Jan 2008
Location: Central Pennsylvania
Posts: 22,556
Rewards Points: 38

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by TimNJ View Post
When I built my place I had my h/w in my mechanical room. After living in the house for a while I ended up relocating it so it was closest to the point of where I actually used most of my h/w. Made a big difference.
That certainly would, no doubt about it.

But it's often not practical to do that for various reasons, and that's when this question comes into play. In the situation that prompted the OP, my buddy ran 3/4" cold water lines, but used 1/2" for hot--based on the theory that the HO wouldn't have to wait as long for hot water at the faucet. The inspector shot him down and made him change it to 3/4".
Tinstaafl is offline  
Old 02-08-2012, 08:01 PM   #32
Working
 
Cole82's Avatar
 
Trade: GC
Join Date: Nov 2008
Location: Cedar Rapids, IA
Posts: 4,131
Rewards Points: 2,276

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Tinstaafl View Post
That certainly would, no doubt about it.

But it's often not practical to do that for various reasons, and that's when this question comes into play. In the situation that prompted the OP, my buddy ran 3/4" cold water lines, but used 1/2" for hot--based on the theory that the HO wouldn't have to wait as long for hot water at the faucet. The inspector shot him down and made him change it to 3/4".
I just tried finding anything that requires a 3/4" line and the only thing I could find are flushing rim sinks.

That is looking at IPC table 604.5

Unless it's a local amendment I would have asked him to show you the code.

Cole
__________________
The boss of awesome
Cole82 is offline  
Old 02-08-2012, 08:06 PM   #33
Capra aegagrus

 
Tinstaafl's Avatar
 
Trade: Remodeler
Join Date: Jan 2008
Location: Central Pennsylvania
Posts: 22,556
Rewards Points: 38

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Cole82 View Post
Unless it's a local amendment I would have asked him to show you the code.
Yeah, I know. But it's the same inspector for framing, plumbing, electric etc etc. Easier to just say yassa, Massa.
Tinstaafl is offline  
The Following 3 Users Say Thank You to Tinstaafl For This Useful Post:
Ben81 (02-09-2012), Cole82 (02-08-2012), mehtwo (03-03-2012)
Old 02-08-2012, 10:30 PM   #34
Chris
 
PowerWash's Avatar
 
Trade: Pressure Washing
Join Date: Mar 2011
Location: Charleston, SC
Posts: 260
Rewards Points: 192

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Tinstaafl View Post
Yeah, I know. But it's the same inspector for framing, plumbing, electric etc etc. Easier to just say yassa, Massa.
And that is the only thing about building new houses I do not miss! Inspectors in our area are assigned a house and they inspect it from start to finish. Gotta play the game.
__________________
Pressure Washing Charleston SC - Pressure Washing Summerville SC Pressure Washing: Charleston, Summerville, West Ashley, Mt. Pleasant, Daniel Island, SC - Pressure Washing
PowerWash is offline  
Old 02-09-2012, 04:05 PM   #35
Registered User
 
Ben81's Avatar
 
Trade: plumber
Join Date: Feb 2012
Posts: 14
Rewards Points: 10

Re: 1/2" Vs 3/4" Hot Water Line


Recirc line 1/2" dia with the pump being 1/2" dia as well. I've seen too many installations with the 3/4" pump and it eventually eating the copper in the house. That type of pump is made for the commercial end of things. This pump is only 1/250th of a hp and has the option to run continuously or on a timer. Timing wise depends where you would hook your recirc line up to. Some instances you can't always get your recirc line teed off right in the cabinet by the affected fixture but put it as close as you can and insulate the recirc line
Ben81 is offline  
Old 03-01-2012, 04:22 PM   #36
New Guy
 
Jackfre's Avatar
 
Trade: General, plumbing, HVAC, solar
Join Date: Mar 2012
Location: N CA
Posts: 20
Rewards Points: 10

Re: 1/2" Vs 3/4" Hot Water Line


There are good reasons to get down to 1/2", from the 3/4" main, as soon as possible. You have to take pressure drop into consideration but I've gone thru this a lot. I represented a major tankless manuf. Tankless will not make hot water until the tap is opened. Proximity to the point of use is a consideration in the installation. Given that the cross sectional area of 1/2" is .19 sq in and 3/4" is .44, there is over twice the vol to possibly waste prior to getting hot water. A properly sized 1/2 line makes sense. Also, you have to consider the flow rate of the particular fixtures you are selling.

On our home in MA. that we sold last year, I had a tankless water heater for 12 yrs. It was right under the kitchen sink. I remodelled the bathrooms and re-installed the tankless on the other side of the basement using the same piping with 3/4 feeding across to the front of the house where the bathrooms were located. It took forever to get hot water at the kitchen sink as I had to dump all that 3/4". I explained to my wife the changes. She then explained to me, not exactly what the changes were going to be, but what the end result would be. After 38 yrs I understand her when she speaks in this way. Especially so when she is correct. I ran a 1/2" line direct to the kitchen sink, reducing the delay and dump vol. All good!
Jackfre is offline  
Old 03-02-2012, 09:23 AM   #37
Pro
 
bob_cntrctr's Avatar
 
Trade: property manager & renovator
Join Date: Jan 2008
Posts: 660
Rewards Points: 500

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Ben81 View Post
Recirc line 1/2" dia with the pump being 1/2" dia as well. I've seen too many installations with the 3/4" pump and it eventually eating the copper in the house. That type of pump is made for the commercial end of things.
Could someone please explain this? A "3/4" pump" (never seen a pump with a 1/2" fitting - but I'm thinking of well pumps) somehow will cause the copper to be corroded?
bob_cntrctr is offline  
Old 03-02-2012, 10:32 AM   #38
Pro
 
txgencon's Avatar
 
Trade: General & Electrical Contracting
Join Date: Jan 2011
Location: Dallas, Texas
Posts: 2,479
Rewards Points: 430

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Inner10 View Post
Think about this, you take a dump, then go to wash your hands with hot water, now the trunk is hot, you get hot water right away at the shower instead of draining long 1/2 inch lines for each fixture.
Who washes their hands just before getting in the shower?

On another note:

100 feet of 3/8" water line will have 0.57 gallons of water

100 feet of 1/2" water line will have 1.02 gallons of water

100 feet of 3/4" water line will have 2.29 gallons of water
txgencon is offline  
Old 03-02-2012, 12:17 PM   #39
Contractor of the Month
 
Inner10's Avatar
 
Trade: Control Systems
Join Date: Mar 2009
Location: Ottawa, ON
Posts: 24,448
Rewards Points: 1,562

Re: 1/2" Vs 3/4" Hot Water Line


I always wash my hand's after wiping my ass...but that's just me.

I'm still surprised to see that running dedicated pipes is common practice in some areas. A popular way lately has been to have a trunk and branch setup with a tankless water heater and a re-circ pump on a timer.
__________________
The Following User Says Thank You to Inner10 For This Useful Post: Leo G
Inner10 is offline  
The Following 2 Users Say Thank You to Inner10 For This Useful Post:
BWFS (03-02-2012), mehtwo (03-03-2012)
Old 03-02-2012, 07:01 PM   #40
Pro
 
txgencon's Avatar
 
Trade: General & Electrical Contracting
Join Date: Jan 2011
Location: Dallas, Texas
Posts: 2,479
Rewards Points: 430

Re: 1/2" Vs 3/4" Hot Water Line


Quote:
Originally Posted by Inner10 View Post
I always wash my hand's after wiping my ass...but that's just me.
You should try using toilet paper and/or wet wipes.

Advertisement

txgencon is offline  
The Following User Says Thank You to txgencon For This Useful Post:
DavidC (03-03-2012)


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nails in Water Line JMK General Discussion 62 01-04-2012 02:05 PM
Comments on replacing tank water heater with tankless CRIMPS Plumbing 3 12-04-2009 11:54 PM
Could water heater be overheating and overflowing? bob_cntrctr Plumbing 18 03-17-2009 07:39 PM
Water Heater noises & air sputtering at faucets LarryS Plumbing 10 01-10-2009 10:41 PM
water line question amurrell Plumbing 15 05-20-2008 08:44 PM

Join Now... It's Fast and FREE!

I am a professional contractor
I am a DIY Homeowner
Drywall Talk is for
PROFESSIONAL CONTRACTORS ONLY!

At DrywallTalk.com we cater exlusivly to professional contractors who make their living as a contractor. Knowing that many homeowners and DIYers are looking for a community to call home, we've created www.DIYChatroom.com DIY Chatroom is full of helpful advices and perfect for DIY homeowners.

Redirecing in 10 seconds
No Thanks
terms of service

Already Have an Account?