Cooling foamy water/pump rattle Is my MCP-600 too powerful?

I just installed a new pump and reservior in my water-cooled setup, and have two (potential) issues.

1) There are very few bubbles in the lines, but when I turn the pump on, everything turns to foam. I'm using distilled H20 w/ water wetter. The water velocity seems rather..umm...vigorous. For example, the bay-res looks only half full when the pump is off. When on, the reservior looks about 90% full (from the front). This is from the water pressure, which causes the water to jet into the reservior and hit the front panel.

2) Kind of a paranoid reaction, really. My two previous pumps worked well for a while, but then developed a "rattle" that really got on my nerves. I had a Via Aqua, then a "Quiet One" (yeah, right). After a while, the noise became enough of a nuisance for me to buy my new swiffy. I'd heard good things about the swiffy, but because I've seen the problem on two different pump models, I'm afraid it'll happen again.

I've debated if this might be caused by the order of my setup. Right now I have:

pump -> water block -> reservoir -> rad -> pump

The only reason for this order is because in my current setup, this is what uses the least tubing. I needed about 5' of tubing, not sure if this is on par with other people or not. I've heard debate about the order in a setup, mostly for the purpose of maximum cooling. My setup has always been excellent as far as performance, so that's not an issue for me. But if my new $60 swiffy develops the same rattle, I'll be very unhappy. Right now, it only puts out a barely percievable hum. The water itself makes more noise (mostly from the reservoir), but this is nothing compared to the racket from my previous pumps.

Anyone have any thoughts?

 

hmm - half full sounds like a bad idea to me - asking for air to get sucked into the pipes when the pump is on....
is this a single or double height bay-res?

 

It might be an idea to get the res immediately before the pump so it gets adequate water supply.

I would hazard a guess that this has been the root of all your previous problems with noisy pumps (noisy pumps.....sorry schoolboy humour )

8Ball amongst others have written about cavitation in the past and i'm sure the thread can't be far away!
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The one thing I will say is that I have never been happy with the idea of a bay res as an airtrap.

It is a product born out of a desire for looks over performance.

The basic design principle of an airtap is a vertical tube with water coming in at the top and out at the bottom. If the diameter of the tube is sufficiently large then the downward velocity of the water flow will be lower than the velocity at which air bubles will rise in water. If the diameter is lower, then the air bubbles will still be pulled into the outlet.

Make sense.

The bayres is a res and not an airtrap.

8-ball

 

Thanks for your advice, guys!

I filled the res a bit more (its a double height 3.5" bay-res), just because that was easy to do. Sure enough, no more foam. I honestly didn't think that would do the trick, since the water level was already above the inlet ports.

The potential for cavitation does worry me somewhat. That's why both my earlier pumps had built-in res/airtraps right at the inlet. Only reason I didn't do this again is because I'm lazy. I had some trouble getting rid of a leak one time, and a home-made res is just more work. So I bought the bay-res because it seemed easier.

Coolmiester, your guess on cavitation would make sense, except that like a said, the earlier pumps had a built-in res. Sure sounded like cavitation, though (from the description in that link you posted). Kinda like marbles rolling around. Another thing I noticed, sometimes when it got really bad, I could jiggle the power cord a few times, cutting power on/off and it would get better for a while. I don't know what the deal was, but I don't believe it was a coincidence. I'm still hoping that it won't happen again.

I'll think about moving around the lines, but won't there be a low-pressure area just before the pump inlet regardless of what the order is? My knowledge of fluid dynamics isn't great, but I think the most important thing is to keep the reservoir as high as possible. It would also probably help to decrease any flow restriction near the inlet. That will be hard to do, since all the fittings (including those coming from the res, and the one on the pump inlet itself) have a smaller diameter than the tubing. It might help to put the res just before the pump, though.

 

You don't have to keep the reservoir at the highest point.

If you are concerned about air bubbles, the velocity of coolant through most tubing/blocks/rads is sufficient to move air bubbles. They will only collect in a scenario as described above for an airtrap.

8-ball

 

Hi 8-ball!

But, I'm not really worried about air bubbles anymore.

To clarify: When I filled the reservoir, the foam/bubbles went away. I don't pretend to be using my bay-res an an airtrap. It just doesn't seem to have been necessary to have an airtrap in this case. It probably wasn't even necessary to have a reservior, but as I've said before, I'm lazy...

I was refering to the potential for cavitation. In my admitedly very limited understanding, cavitation can be caused by low pressure at the inlet, which causes the fluid to vaporize. When the vapor condenses, the action can damage the pump's impeller. I'm trying to figure out if this is what happened to my two previous pumps, and if so, how I can prevent it from happening to my new (and very expensive) MCP-600.

If anyone has any ideas, I'm open to suggestions. Thanks!

EDIT: Maybe I could just take one of the old pumps apart and look at the impellers. If the noise condition was caused by cavitation, shouldn't the impeller look pitted?