# Commercial Domestic Hot Recirc line sizing.



## CaberTosser (Mar 7, 2013)

I know such things are usually undertaken by an engineer, but does anyone have links to sizing tables or charts that can assist in sizing a moderately long domestic hot water recirc line to upgrade a commercial client from their present undersized & inadequate recirc line. I have an excellent local pump supplier that I'm sure will be able to assist me tomorrow, but the independent gremlin in me would love to see some tables and data that I can use to do some calculations for myself. I'm finding pump charts galore, but line size ones are evading me.


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## rjbphd (Feb 5, 2010)

CaberTosser said:


> I know such things are usually undertaken by an engineer, but does anyone have links to sizing tables or charts that can assist in sizing a moderately long domestic hot water recirc line to upgrade a commercial client from their present undersized & inadequate recirc line. I have an excellent local pump supplier that I'm sure will be able to assist me tomorrow, but the independent gremlin in me would love to see some tables and data that I can use to do some calculations for myself. I'm finding pump charts galore, but line size ones are evading me.


 Easy... 1/2 inches.... 1.5 gpm
3/4 ".............. 4 gpm
1" ................ 8 gpm
1 1/4 "......... 14 gpm

Now tell me why the project ur working is undersized?? Most of the hot water return are over engineered, oversized and improper installed..


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## CaberTosser (Mar 7, 2013)

rjbphd said:


> Easy... 1/2 inches.... 1.5 gpm
> 3/4 ".............. 4 gpm
> 1" ................ 8 gpm
> 1 1/4 "......... 14 gpm
> ...


A 4 storey hotel with an underground parkade and 19 - 1/2" drops from various piping risers all tying back into a single 3/4" line with a 220' longest run back to the mechanical room (not including the 4 storeys of elevation) . No proper balancing valves whatsoever, a ghetto attempt to throttle flow to each 1/2" drop using _ball valves _and a multitude of repairs to the lines nearest to the boiler room. Thankfully its all handily accessible in the parkade and there's enough room in the existing unistrut trapeze hangars to run the whole new line ready to tie in to the various drops. The downside is that all those tie-ins will have to be done after midnight when they allow us to drop the domestic water. Due to the fact most of the drops nearest the mech room will be quite thin I'll only be soldering to them, no pro-press or shark-bite or such (those techniques are never up my alley except for use as temporary repairs anyways)

I don't think I'll call this one over-engineered.


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## rjbphd (Feb 5, 2010)

CaberTosser said:


> A 4 storey hotel with an underground parkade and 19 - 1/2" drops from various piping risers all tying back into a single 3/4" line with a 220' longest run back to the mechanical room (not including the 4 storeys of elevation) . No proper balancing valves whatsoever, a ghetto attempt to throttle flow to each 1/2" drop using ball valves and a multitude of repairs to the lines nearest to the boiler room. Thankfully its all handily accessible in the parkade and there's enough room in the existing unistrut trapeze hangars to run the whole new line ready to tie in to the various drops. The downside is that all those tie-ins will have to be done after midnight when they allow us to drop the domestic water. Due to the fact most of the drops nearest the mech room will be quite thin I'll only be soldering to them, no pro-press or shark-bite or such (those techniques are never up my alley except for temporary repairs anyways)
> 
> I don't think I'll call this one over-engineered.


You need to spilt the line coming back to balence it better... have you done hyrodnic heating?... due to pipes nearest the mech room, oversized pump.


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## rjbphd (Feb 5, 2010)

Sorry, I checked ur profile, u have done heating. Pipe it as you would with heating and balancing valves, DOWNSIZE the freaking pump!


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## justme (Jul 4, 2012)

maybe he will post back just how over sized the pump is .


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## CaberTosser (Mar 7, 2013)

Pumps not oversized; heck, I just changed it a while back on one of the handful of line repairs where I wasn't about to reinstall their iron-body unit on the domestic lines. After starting this thread last night I found a good resource in a Canadian copper & brass industry publication.


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## rjbphd (Feb 5, 2010)

CaberTosser said:


> Pumps not oversized; heck, I just changed it a while back on one of the handful of line repairs where I wasn't about to reinstall their iron-body unit on the domestic lines. After starting this thread last night I found a good resource in a Canadian copper & brass industry publication.


Do tell us what size and kind of pump is it.


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