90s, sweeps, or Ts with extensions?

[repairman]

Hi All,
I've notices in pumbing pics some have Ts with about a foot of extended pipe which is then capped instead of just a 90 or a sweep. Does this really create less resistance and is it something I should do?
Thanks,
Repairman

 

[mas985]

It creates less resistance (theoretically) but the change is so small compared to the rest of the plumbing, you would have to have quite a few of those 90s to see a measurable difference. So no, I would not bother.

 

[kadavis]

The better plumbers will run a short piece of pipe and cap off so it evens out the flow along that run. The theory is if you 90 into last return it will Rob more flow away from the others.

 

[mas985]

So exactly how is that better? A TEE branch has twice the head loss than a 90 does but the last run usually has more pipe so you would probably be better off with the 90. Plus the path of least resistance is the previous returns so they are likely to have more flow rate in either case.

 

[repairman]

Thank you both. Has anyone actually A B tested this on the same run of pipe? or on different length runs to see the effect difference?

 

[mas985]

I did a small study on different looping techniques here:

Analysis of Plumbing Loops and Other Configurations

 

[repairman]

Mark,
Quite an in depth "small study." How significant is 1 ft of head loss, or 4 or 5, like on the total symmetry? Does it just use more pump energy, and if you run out of that, slows down flow?
Great stuff, Mark and everyone who contributed to the Analysis of Plumbing Loops... discussion.

 

[mas985]

How significant is 1 ft of head loss, or 4 or 5, like on the total symmetry?

When feeding a set of returns that are asymmetrical but share common nodes (i.e same feed pipe and output to the same pool), it is the flow rate that is different between the paths and head loss must be identical for all the paths because the paths share common input and output nodes.


However, the impact of an increase in head loss on a pump is counter intuitive. An increase in head loss actually reduces a pump's energy consumption as well as flow rate. But the flow rate per watt of energy also decreases so effectively the pump efficiency decreases. But if you don't change the RPM, you still save on energy but sacrifice flow rate which is not always that important.