Expected fluid loss through tubing.

I've been loseing fluid in my watercooling loop, and I know that some tubing is permeable to the point that fluid will be lost. However, pre building my system I figured the fluid loss figure would be neglatable at most. Now it is a different story, the fluid level in my T-line lowers about ~1.5" a month, I'm not sure what to convert it to, tubing is 1/2" ID. I origionally atributed this to bleeding, but all the air should be out after 3 months. Normally I'd not have a problem with this, but I need to start sealing up my system, and having to break the tline cap's seal every month will start consuming a lot of RTV. I'm just wondering if I'm right about this being just fluid loss via tubing or if its some kind of major slow leak that doesn't even let my tracer mark where its going. Could some of it be evaporating out the cap's small air gap? (enough of a gap for air, but not for pure water, so I normally don't worry about it. Unless the water is under pressure.)

You shouldn't be losing that much water. A little seems to be normal. Mine has gone down around an inch in the several months it has been running. 1.5" a month is a little overboard though. Check your system for micro leaks. See if there are traces of dried coolant residue around any fittings. There could also be a small leak in your radiator.

I've checked around w/ my UV light, and Don't see anything currently. I'll try to rember to do it tonight. If I last that long, body is kinda tired after so many changes and lack of sleep of the last week. Leak checking is the only reason I have Highlighter in my loop, so I can see micro leaks.

sunrunner20 said:

Could some of it be evaporating out the cap's small air gap? (enough of a gap for air, but not for pure water, so I normally don't worry about it. Unless the water is under pressure.)

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I think you hit on it. If there is any opening evaporation will occur. I've got a Danger Den fillport sealing the t-line to my res and the o-ring on the fillport does make a good seal. The water in the tube went down maybe an 1/8" in the last 3 months or so since I'd "closed" the system. Some evaporation through the Tygon is inevitable I guess.

if its not evap then your tubing under pressure is expanding slowly

Can it really expand that much?

I don't think it's "expanding" since that implies that it would contract when the pressure was "removed", like when the pump was turned off. I also seriously doubt that any decent tubing like Tygon, Clearflex, MasterKleer, &c would stretch that much as a result of the nominal pressure put out by most pumps (it would have needed to stretch enough to hold the volume of 4.5" of 1/2" tubing which is very unlikely). Like I said above, my water level dropped maybe an 1/8" in three months--I'm using an Iwaki MD-20RZ and Tygon 3603.

Now, a very slow leak somewhere is possible, but if you know the cap doesn't provide a 100% seal, that's probably it. I'd fill it up, seal it, and see if the water level continues to drop. If it does, that would indicate either water escaping the system somewhere (a leak) or air entering the system somewhere (leading to evaporation) that is small and not obvious. If it doesn't drop, problem fixed

3/8 id tygon 3603 with a rbx and 2 maze 4rs and 2 120 rads, laing DDC, when i start the system the water drops in the tline about a inch tygon is pretty soft. When i shut the rig down if the cap is off the tline water will jump out lol.

tygon is soft enough but will resume its original state, [medical grade] with regular tubing it will expand if under enough pressure and just plain stretch. With any heat will make this easier.

again its either evap or stretching if there is no leak its 1 or the other. Tubing will not bleed vynal/plastic is not permeable to water.

if there is the slightest air gap then its evap.

right now my rig's been running for about a week and the t-line drops about 1/4" per day at the moment, but thats easily explained because i still see a few bubbles in my tubing whenever i turn it off (no more water circulating)

i've yet to top it off yet, but it seems that i have fewer air bubbles every day though

I lost about 4" in my T line (DD fill cap) its taken about 5 months... No signs of any leakage anywhere.

and I thought I was the only one well yeah I too have been loosing water overtime, I would say 1-1.5" per month or so, I check for leaks and found nothing, I went over the clamps way too many time and that did nothing. the only thing that I am guessing might be leaking a little bit if any (the system has been running for almost 6 months now and nothing had failed) is my G4 or MCW80 block. anyway I got sick of redoing the system and just decided to add a tea spoon of water every month or so. I am using clearflex by the way 1/2 ID that is.

outhouse said:

Tubing will not bleed vynal/plastic is not permeable to water.

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Actually, Tygon will absorb small amounts of water which will eventually evaporate through the tubing and Tygon is one of the less permeable tubings, evaporation will occur with other types of tubing even faster. But this should still be a very slow process in a completely sealed system and 1-1.5 inches a month is way too much to attribute to evaporation through any commonly used tubing. Here's a link to the abbreviated Tygon spec sheet at Danger Den http://www.dangerden.com/images/misc_hardware/tygr3603.pdf. Check out the absorbtion rate on the bottom of page two.