Cus­tomised PC

Case mods, tools, tech­niques, wa­ter-cool­ing gear and ev­ery­thing to do with PC mod­ding

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PETG vs acrylic tub­ing

I’ve been dab­bling with rigid tub­ing for a few years now, and while in­stal­la­tion does take a lot more ef­fort com­pared with flex­i­ble tub­ing, both clear and metal rigid tub­ing look fan­tas­tic. The straight lines cre­ate a su­per clean­look­ing loop, while clear rigid tub­ing re­ally al­lows your coolant to shine. It can be trick­ier to work with metal tub­ing, and it’s more ex­pen­sive too, but it can also look even bet­ter.

Plas­tic-based tub­ing of­fers another perk, of course, which is that it can be bent to shape to cre­ate a com­pletely cus­tom loop. This tub­ing can be use­ful for cre­at­ing a loop that works specif­i­cally with your hard­ware or case, or for sim­ply cre­at­ing a great-look­ing loop de­sign. There’s a cou­ple of down­sides to acrylic tub­ing, though, which was the first plas­tic-based tub­ing to be­come pop­u­lar with wa­ter­cool­ing en­thu­si­asts. It’s very brit­tle and can crack eas­ily. It’s not an is­sue most of the time, but if your sys­tem is moved, or some­times if a fit­ting is tight­ened too much, the acrylic tube can crack. There are ob­vi­ous consequences to this prob­lem if your sys­tem is filled with coolant at the time.

Acrylic tub­ing has a rel­a­tively high melt­ing point too, which not only re­sults in its brit­tle­ness at room tem­per­a­ture, but makes it tricky to heat and bend, re­quir­ing lots of prac­tice. There is a new kid on the block, though, in the form of poly­eth­yl­ene tereph­tha­late gly­col-mod­i­fied (PETG) tub­ing. In short, PETG tub­ing looks mostly the same as acrylic tub­ing and comes in the same sizes. How­ever, it has one key prop­erty that makes work­ing with it much easier – it has a lower melt­ing tem­per­a­ture, which means you can heat and bend it far more eas­ily.

More im­por­tantly, though, early tests showed what ap­peared to be an in­cred­i­ble re­sis­tance to shat­ter­ing com­pared with acrylic tub­ing. The lat­ter will eas­ily shat­ter us­ing a ham­mer, but by con­trast, a ham­mer will likely bounce off an iden­ti­cal piece of tub­ing made from PETG. The lower melt­ing point not only means it’s easier to bend, but also that it’s closer to a liq­uid state at room tem­per­a­ture than acrylic tub­ing, mak­ing it more elas­tic and crack­proof as a re­sult.

It’s no won­der, then, that many man­u­fac­tur­ers have fo­cused on PETG tub­ing as their pri­mary tub­ing, in­clud­ing Ther­mal­take, which has been busy re­leas­ing its own large range of wa­ter-cool­ing gear re­cently. For the most part, it was a wise de­ci­sion. It’s easier to work with PETG tub­ing, and of course it’s far more shat­ter­proof.

How­ever, you’ll note that I don’t say that it’s stronger than acrylic tub­ing, which is true. It doesn’t have a

molec­u­lar struc­ture that’s phys­i­cally stronger or stiffer, its ben­e­fits are purely down to its lower melt­ing point and the fact that it’s closer to be­ing a liq­uid at room tem­per­a­ture.

Un­for­tu­nately, the lower melt­ing point does pose one sig­nif­i­cant is­sue. At room tem­per­a­ture, PETG tub­ing is tough enough to han­dle any job a liq­uid-cool­ing loop can throw at it. How­ever, hor­rific pho­tos have ap­peared on­line of the tub­ing seem­ingly bent out of shape and com­pressed, even in­side the com­pres­sion fit­tings them­selves.

It’s a situation that has led to leaks, but it’s im­por­tant to un­der­stand why the tub­ing acted in this way. In each case, or at least cer­tainly the ones I’ve read about any­way, there has been a fairly clear rea­son for this be­hav­iour. A fail­ure in the sys­tem, specif­i­cally a pump or fans, will see the coolant tem­per­a­ture sky­rocket, but it might then take sev­eral min­utes be­fore your PC ac­tu­ally crashes. By then, the dam­age will have been done.

Much more wor­ry­ingly, the coolant tem­per­a­ture can get too high even in a work­ing, sta­ble sys­tem. Li­nustechtips fo­rum user Smol­lie1 re­vealed that his small form fac­tor wa­ter-cooled PC, built into a Frac­tal De­sign Node 202 case, sud­denly sprung a leak. On closer in­spec­tion, his PETG tub­ing had be­come com­pressed in the fit­tings due to high coolant tem­per­a­tures. This com­pres­sion was sim­ply caused by a lack of air­flow in a small, cramped

sys­tem, but the is­sue is that the CPU and GPU tem­per­a­tures were well away from their ther­mal lim­its.

Their tem­per­a­tures were very high for a cus­tom wa­ter-cooled PC, though, with the GPU ap­proach­ing 70°C un­der load, in­stead of a more typ­i­cal tem­per­a­ture of 40-50°C for a wa­ter­cooled GPU, and the CPU tem­per­a­ture be­ing even higher. For nor­mal flex­i­ble tub­ing, and prob­a­bly acrylic tub­ing too, these tem­per­a­tures would likely be fine, but un­for­tu­nately, PETG tub­ing can start to lose its shape at these tem­per­a­tures, whereas acrylic tub­ing gen­er­ally isn’t affected in this way.

It’s not just a case of avoid­ing pump or fan fail­ure, which isn’t com­mon but far from a rare oc­cur­rence, es­pe­cially with Laing DDC-based pumps. It’s mainly down to be­ing aware if your PC’s wa­ter-cool­ing sys­tem will be op­er­at­ing at higher tem­per­a­tures than usual – for ex­am­ple, in a small form fac­tor PC. There’s a bit of fore­thought re­quired if you plan to use bend­able, plas­tic-based tub­ing. It’s trick­ier to

work with acrylic tub­ing, and it’s more prone to shat­ter­ing, although it will be fine in 99.9 per cent of sit­u­a­tions.

How­ever, if you’ve seen the var­i­ous ham­mer-test videos on­line, which com­pare PETG with acrylic tub­ing, it’s im­por­tant to re­alise that PETG isn’t stronger, and the lower melt­ing point means you need to be aware of your coolant tem­per­a­ture as well. If you have a nor­mal tower PC with am­ple ra­di­a­tor cool­ing ca­pac­ity, you need to have an ac­tive warn­ing sys­tem for pump or fan fail­ure.

In ad­di­tion, in sys­tems that might be op­er­at­ing at higher coolant tem­per­a­tures (such as small form fac­tor rigs), it would be wise to in­vest in a fan con­troller such as Lamptron’s CW611, which has the abil­ity to mon­i­tor coolant tem­per­a­ture and ramp up fan speeds when re­quired. Ther­mal­take states that its PETG tub­ing will start to be­come mal­leable at 62°C, so you’ll want to keep your coolant at least 15°C be­low this tem­per­a­ture un­der load if you use PETG tub­ing.

Our re­cent dream PC build used PETG tub­ing, and work­ing with it was com­par­a­tively easy

A fan con­troller that re­acts to coolant tem­per­a­ture would be a wise in­vest­ment if you’re us­ing PETG tub­ing

PETG tub­ing can end up be­com­ing com­pressed in tube fit­tings at high coolant tem­per­a­tures, caus­ing leaks, as shown in this photo from Li­nustechtips fo­rum user Smol­lie1

Rigid tub­ing uses sim­i­lar com­pres­sion fit­tings to nor­mal tub­ing

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