Quick GPH double check

[kibbler]

Emailed Geminicool a couple of questions, one of which was which version of the CPU WB I should use with my pump, Eheim 1048 listed at 158GPH

Edit:
Normal flow version: .042in^2 channel cross section
High flow version: .072in^2 channel cross section

He replied (excerpt):

"Typically, when system flow is measured, it's about 1/3 that of the actual pump rating. I would estimate your max system flow at about 60-80gph. Given this, I would recommend the low flow unit to be used with the pump you specified"

I really don't mean to second guess him, I mean he was nice enough to reply, but does that 1/3 flow theory hold water, so to speak? (heh)

Geminicool looks like they have pretty good business going, bunch of nice products.

thx!

[Can O' Beans]

That GPH is the MAX that pump can do. Meaning NO flow restriction, etc...

If you put that in a WC system, it will then have restrictive tubing, radiators, 90 deg turns, and waterblocks to slow the flow down a lot.

[Volenti]

I really don't mean to second guess him, I mean he was nice enough to reply, but does that 1/3 flow theory hold water, so to speak? (heh)

In a "normal" CPU-rad-pump setup that hasn't been specificly optimized for flow then I'd say 1/3-1/2 of rated flow would be about right.

But...a lot depends on what is in the system, hose size, pump size, water block design, rad ect..

Take my current system, 1/2'' tubing (4' worth) close to 0 vertical head, and a DIY block specificly designed to be low restriction.

I have a small 700L/H pump running this, and I'm getting ~500L/H flow, that's 71% efficiency.

If I hook up my 2800L/H pump (same brand) to this setup I get ~900L/H, that's only 32% efficiency, on an other wise identical setup simply by changing the pump.

I'd personally get the high flow block my self.

[bigben2k]

Actually, the low flow will not require a higher flow to perform as well as the high flow version.

For an Eheim 1048, the low-flow is probably best.

What's interesting is that for all the restrictions in a rig, most of which comes from the waterblock (unless one has lots of elbows), the effective flow rate that most people get is less than 100 gph, and few of them seem to know this!

[decodeddiesel]

I'd say 1/3 may be rather high depending on what was said before like block type, # of 90 degree fittings, length of tubbing, vertical rise of the system (head), ID of tubbing/ID of fittings, etc. All have an impact on your overall flow.