Best bang for buck on indirect DHW tanks

[BrownianHeatingTech]

Hi Joe are the inside diameters of PEX pipe not true to their size? If I do the math using their stated sizes, the area of three 3/4" pipes is larger than the area of a 1 1/4' pipe.


A = 3.14*r*r
3/4 = .75 R = .375
Area = 3.14*.375*.375 = .4415625 x 3 = 1.3246875" 3 Runs is more than 1 1/4 pipe

1 1/4 = R = .625
Area = 1.22656"

If its small hopefully it wont matter, I could go with all 1", just trying to save on having to buy multiple rolls of PEX and only using partial of each and wasting money.

Most pex isn't exactly the listed diameter, but that's not the issue.

Circumference of 1 1/4" pipe is 3.927" - total circumference of three 3/4" pipes is 7.096". The greater circumference means greater surface area, which means more friction. It's a non-linear relationship, so despite the fact that the 3/4" pipes have 180% the surface area of the single 1 1/4" pipe, the friction is only about 10% higher for the 3/4" setup.

Absolute maximum flow is not the issue in piping - how much friction you have, is, as that determines the pump size.

Joe

 

[mpilihp]

Hi Joe its much deeper im guessing than my brain can go in a few min. I get the idea that there is more internal pipe surface area with three 3/4" runs than one 1 1/14" pipe and so that friction is going to restrict the flow of water when compared between the two setups using the same size pump. Its a wag I know and just trying to get in the ball park. If going with two 1" PEX runs is better (less surface area) then I can do that, my thought was to also have multiple connections in/out of the storage tank to reduce the flow at any one point and increase the chances of better stratafication. IE across the top of the tank have three connections spread out, same on the bottom. I could do two runs and then split each of them into two connections into the tank...

 

[BrownianHeatingTech]

Hi Joe its much deeper im guessing than my brain can go in a few min. I get the idea that there is more internal pipe surface area with three 3/4" runs than one 1 1/14" pipe and so that friction is going to restrict the flow of water when compared between the two setups using the same size pump. Its a wag I know and just trying to get in the ball park. If going with two 1" PEX runs is better (less surface area) then I can do that, my thought was to also have multiple connections in/out of the storage tank to reduce the flow at any one point and increase the chances of better stratafication. IE across the top of the tank have three connections spread out, same on the bottom. I could do two runs and then split each of them into two connections into the tank...

I'm not sure how you would have multiple connections to the tank. The tank only has certain tappings.

Joe

 

[mpilihp]

Im going to have threaded ports (weldets others have called them) welded in. THeres one that is damaged and needs to be replaced/welded over anyhow so welding will be needed so I figured Ill get several welded on. A project for next summer as I need to locate a welder, the local one I used to rely on has moved away.

~ Phil