Water Loop Physics Question

[GearingMass]

Ok so this might be an odd question, but I don't want to regret this potentially happening when I build my first custom loop.

I'm going to have, among other things, a dual bay reservoir, and a 360 rad in the top of my case, so the reservoir will not be the highest point in the case.

My question is - wait I should probably preface this by saying that the reservoir has the pump built in, and the pump outlet will be going straight over to the CPU, and then up to the top rad.
Anyway, upon filling the loop, once the loop is pretty full, once the pump stops, since there's water in the top rad, and the reservoir is not the top item in the loop, will the water above the reservoir start making it's way to the reservoir, overflowing it? Kinda like poking a hole in a water bottle - the water has a way to lower it's potential energy so it takes it. Is this going to happen with the loop? Will the water above the reservoir makes it's way to the reservoir, fill it up, and overflow it?

I'd rather not flood my system, and I've been ignoring physics in my loop consideration up until now. Haha
But plenty of people have top rads, so surely there's a solution if this is, in fact, a problem.

 

[Bishoff]

Ok so this might be an odd question, but I don't want to regret this potentially happening when I build my first custom loop.

I'm going to have, among other things, a dual bay reservoir, and a 360 rad in the top of my case, so the reservoir will not be the highest point in the case.

My question is - wait I should probably preface this by saying that the reservoir has the pump built in, and the pump outlet will be going straight over to the CPU, and then up to the top rad.
Anyway, upon filling the loop, once the loop is pretty full, once the pump stops, since there's water in the top rad, and the reservoir is not the top item in the loop, will the water above the reservoir start making it's way to the reservoir, overflowing it? Kinda like poking a hole in a water bottle - the water has a way to lower it's potential energy so it takes it. Is this going to happen with the loop? Will the water above the reservoir makes it's way to the reservoir, fill it up, and overflow it?

I'd rather not flood my system, and I've been ignoring physics in my loop consideration up until now. Haha
But plenty of people have top rads, so surely there's a solution if this is, in fact, a problem.

How would it flood? Does the rez have an open valve? If so then yes it will leak out.

 

[ShrimpBrime]

I like to pump to the Rad then to the Cpu and then a rad after the cpu. Thus cooling heat after and then before the cpu sees the liquid in the block.

 

[GTXJackBauer]

What you want to do is have many towels around in all areas just in case. You'll want to first fill the loop and "bump" the pump, meaning turning it on and off when the fluid has left the reservoir or prior to that state since you don't want the pump running dry. Once you get to the point where the reservoir fills up when you shut off the pump because some of the fluid if not most will enter its way back into the reservoir, you'll want to keep the pump on continuously, assuming the pump is consistently primed and fill the reservoir up once it lowers a bit. While its on you'll want to make sure you close the reservoir at that point. Run the pump this way for a few hours as the bleeding will still be in process. If you're water levels get low when your pump is off than proceed to fill it some more but make sure when you unscrew the reservoir cap that the pressure build up in the loop will be released and that doesn't have the liquid spilling out but by that time you'd know you've lose some fluid over time and shouldn't be a issue. You'll want to move the case around a bit to a angle where the reservoir is raised up a bit should help in the bleeding process but eventually the bubbles can make their way back into the reservoir over time.

I hope this helps.

 

[GearingMass]

How would it flood? Does the rez have an open valve? If so then yes it will leak out.

This is the res/pump combo. The fillport is on top. Will it leak out of that if the top port isn't closed? And is that top port waterproof?

How do people normally fill reservoirs that are not the top of the loop?

 

[GearingMass]

What you want to do is have many towels around in all areas just in case. You'll want to first fill the loop and "bump" the pump, meaning turning it on and off when the fluid has left the reservoir or prior to that state since you don't want the pump running dry. Once you get to the point where the reservoir fills up when you shut off the pump because some of the fluid if not most will enter its way back into the reservoir, you'll want to keep the pump on continuously, assuming the pump is consistently primed and fill the reservoir up once it lowers a bit. While its on you'll want to make sure you close the reservoir at that point. Run the pump this way for a few hours as the bleeding will still be in process. If you're water levels get low when your pump is off than proceed to fill it some more but make sure when you unscrew the reservoir cap that the pressure build up in the loop will be released and that doesn't have the liquid spilling out but by that time you'd know you've lose some fluid over time and shouldn't be a issue. You'll want to move the case around a bit to a angle where the reservoir is raised up a bit should help in the bleeding process but eventually the bubbles can make their way back into the reservoir over time.

I hope this helps.

Kinda, yes.

I'm still trying to figure out though - whenever the pump is off, will the water above the res come back down until the reservoir is 100% full, and will this leak out of the top fill port, or is the top plug waterproof?

 

[GearingMass]

GTX I just looked through your 900D build log and noticed you have one reservoir in/out going straight up to your top radiator - so if what I'm asking about is true, then you should have experienced the same thing.

Does your reservoir fill up to 100% when your pump is off?

 

[ShrimpBrime]

Kinda, yes.

I'm still trying to figure out though - whenever the pump is off, will the water above the res come back down until the reservoir is 100% full, and will this leak out of the top fill port, or is the top plug waterproof?

Fill the water system until completely full the cap it. Seal it. If the fill post plug has a gasket, you know the little rubber o-ring, then yes, that would be a sealed closed loop. No water should escape.

If the Res in at the top, and the fill post is the top most point, then gravity will stop the liquid from coming out when the system is off.

Currently running an open loop res and the bottom with the fill line which is about 3 feet long doesn't leak when the system is off. Vacuum I think stops the leak. There's only one hole and my bleeder is closed.

 

[GearingMass]

Fill the water system until completely full the cap it. Seal it. If the fill post plug has a gasket, you know the little rubber o-ring, then yes, that would be a sealed closed loop. No water should escape.

If the Res in at the top, and the fill post is the top most point, then gravity will stop the liquid from coming out when the system is off.

Currently running an open loop res and the bottom with the fill line which is about 3 feet long doesn't leak when the system is off. Vacuum I think stops the leak. There's only one hole and my bleeder is closed.

I'm concerned with how fast the water level will rise and if it'll be trouble getting the fill plug on in time before the water level rises to the top of the res when the pump is turned off.

The res won't be the top-most point of this loop, though.

I'm having a hard time picturing your loop.

 

[GTXJackBauer]

GTX I just looked through your 900D build log and noticed you have one reservoir in/out going straight up to your top radiator - so if what I'm asking about is true, then you should have experienced the same thing.

Does your reservoir fill up to 100% when your pump is off?

Yes, it actually spilled out a bit but had my shammys in hand. The reservoir lowered once the pumps were turned on and the fluid circulated as I filled it up once more towards the top, plugged it, turned off the pumps and was good to go. As long as you have a good seal it won't matter than. Just make sure you don't turn off the pumps while you topped off the fluid prior to them running with no plug on.

I was hoping my big paragraph didn't confuse you but this statement should be easier to understand and knowing you've seen my rig's top rad and res/pump combo should make things easier now.

 

[GearingMass]

Yes, it actually spilled out a bit but had my shammys in hand. The reservoir lowered once the pumps were turned on and the fluid circulated as I filled it up once more towards the top, plugged it, turned off the pumps and was good to go. As long as you have a good seal it won't matter than. Just make sure you don't turn off the pumps while you topped off the fluid prior to them running with no plug on.

I was hoping my big paragraph didn't confuse you but this statement should be easier to understand and knowing you've seen my rig's top rad and res/pump combo should make things easier now.

Yep I think I have a clearer picture of what needs to happen now. As long as my top fill port cap has a good seal on it, everything should be A-Ok.

 

[GTXJackBauer]

Yep I think I have a clearer picture of what needs to happen now. As long as my top fill port cap has a good seal on it, everything should be A-Ok.

 

[RnRollie]

just use a multiport radiator at the top, so you can fill/bleed through that radiator.

Or replace the fillport of the reservoir with this: http://koolance.com/vlv-vl002k-pressure-valve

 

[Diggrr]

Water shouldn't be able to come down from the top radiator unless air is allowed to go up to it. Water is a non-compressable fluid.
So as long as you don't run the res almost empty to the point of the hose barb being above the waterline when you're filling/bleeding, you'll be alright to open it to add more. Tip the system backwards if necessary to keep the tubing inlet below water to open it safely.

It's soft tubing that let's the water level vary between running and off...the tubing swells slightly in front of restrictions, thus increasing it's volume. When the pump is off, the tubing shrinks back to normal size, thus raising the water level.

 

[Owenator]

You could replace the fill port with a barbed connection and run a tube up from there to above the rad. I use a strategy like this and then cap the tube. I can then see how the level changes when the pumps are on or off.

 

[Bishoff]

This is the res/pump combo. The fillport is on top. Will it leak out of that if the top port isn't closed? And is that top port waterproof?

How do people normally fill reservoirs that are not the top of the loop?

I see...can't tell from the pic, but is there an o-ring on that cap? That would definitely have me worried if it's not a sealed type of cap.

 

[GearingMass]

just use a multiport radiator at the top, so you can fill/bleed through that radiator.

Or replace the fillport of the reservoir with this: http://koolance.com/vlv-vl002k-pressure-valve

Well already order the radiator. The AX360 does not have multi ports.

And that isn't the problem I'm concerned with. The problem isn't built up pressure, it's water filling up the res when it's open because it's not the highest point in the loop.

Water shouldn't be able to come down from the top radiator unless air is allowed to go up to it. Water is a non-compressable fluid.
So as long as you don't run the res almost empty to the point of the hose barb being above the waterline when you're filling/bleeding, you'll be alright to open it to add more. Tip the system backwards if necessary to keep the tubing inlet below water to open it safely.

It's soft tubing that let's the water level vary between running and off...the tubing swells slightly in front of restrictions, thus increasing it's volume. When the pump is off, the tubing shrinks back to normal size, thus raising the water level.

To your first paragraph, I think that's exactly what I was looking to hear. That's a very good point, as long as the in/out ports are submerged, the water hopefully won't "fall" down into the reservoir. I think that's how that works (I haven't quite taken fluid dynamics yet ).

To your second point, that's a good think to keep in mind.

You could replace the fill port with a barbed connection and run a tube up from there to above the rad. I use a strategy like this and then cap the tube. I can then see how the level changes when the pumps are on or off.

I might do that if it becomes a problem, but hopefully not. Storing that extra tube above the res in the case would be unsightly and a hassle.

I see...can't tell from the pic, but is there an o-ring on that cap? That would definitely have me worried if it's not a sealed type of cap.

I'll probably shoot Swiftech an email to check on that.

 

[Diggrr]

To your first paragraph, I think that's exactly what I was looking to hear. That's a very good point, as long as the in/out ports are submerged, the water hopefully won't "fall" down into the reservoir. I think that's how that works (I haven't quite taken fluid dynamics yet ).

Me either, but I've been here long enough, and soaked my floor enough to learn a thing or two! I was water cooled for months before I joined in '01.

The weight of a cup of water isn't enough to draw a hard vacuum on the air traveling upward, so as the long as the other end of the air supply tube is blocked by water, the water trying to come down from the rad can't.
You can tip your system on it's back and pull the bay res out of the front to sit it level while you fill too...that puts it at the highest point, so no worries!
Been there, done that.

 

[bob4933]

Ignoring pretty much everything else...


Pumps operate on pressure curves. If the pump is built into the reservoir, it will not matter where it's physical location is, because the pump is designed to operate under the reservoir.

Now if you had a standalone pump, it would be ideal to mount it at the lowest point in the system to give it the most net positive suction head. Centrifugal pumps raise capacity with more NPSH, and won't cavitate under normal operations. I imagine there will be a minimum fill level marked on your reservoir. Keep fluid levels above that, and you will have no issues.

The next question, is your pump rated to push the amount of water that 2 reservoirs will have? As long as your radiator is performing it's function properly, you shouldn't need anything more.

 

[GearingMass]

Me either, but I've been here long enough, and soaked my floor enough to learn a thing or two! I was water cooled for months before I joined in '01.

The weight of a cup of water isn't enough to draw a hard vacuum on the air traveling upward, so as the long as the other end of the air supply tube is blocked by water, the water trying to come down from the rad can't.
You can tip your system on it's back and pull the bay res out of the front to sit it level while you fill too...that puts it at the highest point, so no worries!
Been there, done that.

Perfect! Sounds like a solution.

Also, while I've got everyone here, would you recommend adding some extra length to the two tubes that go to/from the reservoir so that it can be pulled out of it's bays while still attached to the loop?