Is a Reevoir necessay in a H2O cooling system??

[strokeside]

If you already have a pipe design that allows for bleeding and refilling, do you really need a resevoir in your system?

[WarriorII]

No.

As long as you have enough H20 while it is running.

[stool]

Not necessarily, but you would probably want to have a good-sized radiator to allow for a bit more cooling of your water.

[Spartacus51]

A res is not necessary, but can be helpful. Having one allows for more water, thus more space for the heat to disapate into. It will allow for warm water to be cooled to some extent. Not needed, but probably helpful.

[res0r9lm]

having res will take it longer for water temps to equalize heck if you wern't going to run 24/7 you could get by without rad with a huge res. had a 5 gallon res on one system took 2 days for the water to get hot without rad.
advantages of using res is easy filling & bleeding, can tell where water level is, more versitle... ability to add 2nd pump(high flow for waterblock & slower flow for rad) using only one pump is a compamize between rad and block

[Unkle_Freeze]

The main reasons for using a res have already been covered in this post quite well, but one of the advantages with a closed system is that you can mount your radiator remotely, without having to comply with the pump's maximum lift height.
By this I mean, If your pump has a !.5m lift height, this means 1.5m into free air, if the system is closed you will have a negative pressure displacing any weight of fluid that the pump has had to lift so your pc could be on the ground floor and the rad in your attic/loft with no (or little) loss of flow.
At least this is what i have found.

[res0r9lm]

thanks for info. I'm in the middle of building an inline system myself.

[Diggrr]

The main advantage I've found in using a reservior is that I was constantly tinkering with the system, so I would have to wait a day to bleed out all the air bubbles everytime I changed something out. I like to use a very small amount of dishsoap in the water, so the bubbles would turn to foam quickly, and take seamingly forever to work out of the bleeder line.
I can't really say that having one now will stabilise my temperatures, as I don't use a temperature monitor in the water system. The cpu reaches the ususal idle temp as fast as I can boot and get into bios though. My res holds about a quart and a half, and I have 15-20 feet of water line.
You can make a sort of reservior to help bleed out the air out of almost anything. You can also make it compact enough to fit in a very small case. I've even seen some people use 1" pvc "t"s with a cap on one leg.

I don't use a closed loop system anymore only because of my situation. Your's will be different, so think ahead to what you want to do, and choose based on that. If you're going to setup and leave it, a bleeder 't' will work great for you.