Question Custom loop - air bubbles keep on coming back..

[gijoe50000]

So I built my system about 6 months ago and I did the usual tilting the case, and running the pump, to get rid of air bubbles, and I thought I had most of the bubbles out of it.
But ever since I still have bubbles in the system.

For example, if I run the pump at high speed I'll get gushing bubbles for a minute or two, and they'll eventually disappear; but then the next day I'll do the same and get more bubbles again. And again, and again.
It's not like normal where you get less and less bubbles, as you gradually bleed the system, for me it seems like they constantly "build up" in the system and release when I run the pump at high speed..
It's like a new, unbled system every day!

My temps are fine, so I doubt that I have huge air pockets in the system, although I can't totally rule it out, but to me it seems like air is getting into the system some other way, like overnight when the system is turned off or something.
I know it sounds kind of weird, but I can't think of any other explanation.
My water levels are not dropping, so I doubt I have a leak in the system.

I also don't have anything crazy going on with the location of the components, it's all pretty standard (see the image below).

Has anybody ever come across something like this, or have any idea why I'm getting bubbles in the loop after 6 months?
I'm using ordinary distilled water in the loop, and an antimicrobial additive, same as I did in my last system.

Just today, for example, I ran the pump at full speed for a few minutes and I got loads of bubbles rushing down into the res for about 2 minutes, and they eventually stopped. But I'm pretty sure that if I run the pump at full speed tomorrow the same thing will happen.
I've been watercooling for a good few years now and never came across something like this.. It's strange.

 

[Eximo]

I wouldn't rule out trapped air bubbles somewhere in the loop. When the pump isn't running, they collect somewhere. When the system turns on it has to push out the one large bubble and churns them up into small bubbles when they pass through the pump until they regather in the same spot as they circulate.

Run with the reservoir open so there is no excess pressure in the loop.

If possible lay the system in a different orientation while you have it running, see if you get different behavior.

 

[gijoe50000]

I wouldn't rule out trapped air bubbles somewhere in the loop. When the pump isn't running, they collect somewhere. When the system turns on it has to push out the one large bubble and churns them up into small bubbles when they pass through the pump until they regather in the same spot as they circulate.

Run with the reservoir open so there is no excess pressure in the loop.

If possible lay the system in a different orientation while you have it running, see if you get different behavior.

Thanks, just done that there, and I'll see how it goes.
I blasted the pump again just now, and it had a sudden large burst of bubbles initially, which does seem like a large air bubble breaking up.
I'm not totally ruling out the idea of air still being in the system after the initial filling, but it just seems like too much air over the last 6 months. At least compared to my previous loops. Generally after 2-3 days you'd have all the air out of the system.

But yea, I know what you mean about bubbles building up in places, I've seen that happen a lot, and you can sometimes see it visually in the tubing as the bubbles float back to a "nice" spot when you turn the pump off, or if the pump isn't fast enough to force the bubbles through a particular configuration.

I suppose it's also possible that some of the air bubbles get forced down through the pump again when I run it at full speed, the D5 pumps are quite powerful, although it does seem that the vast majority of them bubble to the surface, and I do open the filler cap from time to time to release pressure.