how many 3/4'' pipes goes into an 1'' pipe or 1 1/4'' pipe?


Old 11-15-14, 02:21 AM
Thread Starter
Join Date: Mar 2011
Location: USA
Posts: 106
Received 0 Votes on 0 Posts
how many 3/4'' pipes goes into an 1'' pipe or 1 1/4'' pipe?

how many 3/4'' pipes goes into an 1'' pipe or 1 1/4'' pipe? i know 3/4'' is double capacity of 1/2'' but want to figure out how many 3/4'' pipes goes into an 1'' pipe or 1 1/4'' pipe? i am wandering if tankless water heaters can be paired up for a radiant heat system and a couple of tankless water heaters can be connected to make 1'' pipe? say 2 50,000 btu water heaters paired up to make 100,000 btu for 1'' pipe. is there a chart that shows doubling pipe capacity?
Sponsored Links
Old 11-15-14, 02:44 AM
pugsl's Avatar
Forum Topic Moderator
Join Date: Mar 2008
Location: United States
Posts: 9,029
Received 74 Votes on 67 Posts
Google: pipe volumn chart here is one of the first one's I found
Water Content in Pipes
Old 11-15-14, 07:03 AM
Join Date: Jan 2010
Location: North East Kingdom of Vermont
Posts: 2,533
Received 1 Vote on 1 Post
That's a good chart; but if a computer isn't right handy, it's good to know the basis on which the chart was built, all using that old formula for the area of a circle - ΠR or 3.1416 X the Radius X the Radius. So for the pipes you were interested in, the ratios are as follows:

" Pipe = ΠR = 3.1416 X ⅜ X ⅜ = 0.442 Square Inch;

1" Pipe = 3.1416 X X = 0.7854 Square Inch;

1" Pipe = 3.1416 X ⅝ X ⅝ = 1.227 Square Inch.

Multiply these Square Inch areas by 12 inches and you get the Cubic Measurements shown in Pug's Chart.
Old 11-15-14, 10:16 AM
NJT's Avatar
NJT is offline
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I usually use a general 'rule of thumb' that up to 1-1/4 pipe size, you can use two of the next smaller size into one.

In other words, two 1/2 into one 3/4;

two 3/4 into one 1;

four 1/2 into one 1;

two 1 into one 1-1/4;

four 3/4 into one 1-1/4;

eight 1/2 into one 1-1/4;


After 1-1/2, the differences get larger... see chart that pugsl posted.
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

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: