If you can read the pump RPMs, do you still need a flow indicator?

VirtualMirage

Limp Gawd
Joined
Nov 29, 2011
Messages
333
The title pretty much says it all. I am building a custom loop and I am trying to determine if a flow indicator is still a necessary investment if I end up going with a PWM controlled pump which *should* be able to report back the pump RPMs. Am I assuming correctly on this?

If so, then is a flow indicator still recommended or even necessary if that is the case?
 

Zarathustra[H]

Fully [H]
Joined
Oct 29, 2000
Messages
30,802
You never NEED a flow indicator.

It's just a nice to have to confirm that you are getting the flow tyou think you are getting.

RPM is not 1:1 with flow rate. It will depend on the restrictiveness of the loop
 

VirtualMirage

Limp Gawd
Joined
Nov 29, 2011
Messages
333
Thanks for the quick answer.

Any particular flow indicator that you recommend that is quiet and reliable?

I have read a mixed bag of reviews of a couple out there already. Some seem to stop moving after a while and others that seem to be dependable can be noisy or rattle.
 

jlewis02

n00b
Joined
Aug 23, 2020
Messages
44
Save the money for a flow indicator for something else.
They will all stop working at some point and they will restrict flow to a small degree.
 

Nimisys

Fully [H]
Joined
Jun 20, 2000
Messages
18,654
The cheap pinwheel flow indicators are almost a waste of money. They will work long enough to give you confidence in your loop, then eventually get stuck causing both an un-needed restriction and panic.

That being said, the scientific/industrial meters will last much, much longer and give you an actual number, but they are 100$+ on the low end for the unit, let alone a display.

From experience with a failing MCP35x pump, if it fails, you'll notice a sudden rise in temperature, even at idle. With a large enough loop, you will be able to shutdown all on your own, otherwise the safety shutdown takes place.
 

BrotherMichigan

Limp Gawd
Joined
Apr 8, 2016
Messages
281
That being said, the scientific/industrial meters will last much, much longer and give you an actual number, but they are 100$+ on the low end for the unit, let alone a display.

You can get differential pressure flow sensors (no moving parts) for a bit over $50, so it's not quite that bad.
 

THRESHIN

2[H]4U
Joined
Sep 29, 2002
Messages
3,184
Honestly I've never bothered with flow indicators. I can clearly see the fluid is moving in my reservoir and with temp protection these days the worst that will happen (in theory) is the system will shut down.

Pump rpm is a nice touch. As stated, it's not necessarily a direct indication of flow but it might help with pump health. Also just listening to the pump will help. If the tone of the motor noise starts to change or you hear things like ticking it's probably time to get a new pump.
 
Joined
Apr 5, 2016
Messages
2,195
Flow indicators are useless eye candy.

Flow meters, on the other hand, are the only way to correctly protect a watercooled system at the BIOS level. If your loop clogs, you may lose flow without your pump actually failing. Pump spinning ≠ flow.

The output of a flow meter can be plugged into your CPU_FAN header, and thus if you have no flow on startup, your BIOS will protect your system by refusing to boot. If you're using software, you can configure an emergency shutdown on loss of flow.
 
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