Pex really scale proof?

[Treeman]

I have a 100', 1/2" polyethylene tube bleed line off my greenhouse evaporative cooling pads (15 psi, low flow). After about 5 years, the scale build up breaks off and clogs the line and I have to replace it (2 hours of work, no biggie).

Would pex alleviate this problem? The mfg. hype says it is scale "resistant" (usually compared to copper). Several local plumbing supply house knoweledgeable people say that with this mineral laden water, the pex might be a little better, but it would NOT solve the problem (scale flaking off and clogging).

The pex is 2 x more $ and I have to be careful about sun exposure. Cost is not an issue, but I also don't want to invest a bit more time and $ if this is not the "silver bullet".

Comments about scale build up?? Thanks!!!!!

 

[Redwood]

the scale resistance of PEX is probably comparable to the polyethylene you are using.
PEX after all is a cross-linked polyethylene tube. In addition the PEX has problems with exposure to sunlight and it's UV light.

 

[Sponsor]

 

[Gary Slusser]

I have a 100', 1/2" polyethylene tube bleed line off my greenhouse evaporative cooling pads (15 psi, low flow). After about 5 years, the scale build up breaks off and clogs the line and I have to replace it (2 hours of work, no biggie).

Would pex alleviate this problem? The mfg. hype says it is scale "resistant" (usually compared to copper). Several local plumbing supply house knoweledgeable people say that with this mineral laden water, the pex might be a little better, but it would NOT solve the problem (scale flaking off and clogging).

The pex is 2 x more $ and I have to be careful about sun exposure. Cost is not an issue, but I also don't want to invest a bit more time and $ if this is not the "silver bullet".

Comments about scale build up?? Thanks!!!!!

Half inch PEX will have a smaller ID, and thereby be more prone to blockage. Why not 3/4" poly which shouldn't block up as easily? Or install a tee and flush the line with more higher pressure water from a garden hose every so often?

 

[Treeman]

Gary, that was my very first idea also, but others told me just the opposite. They said that going to a smaller I.D. will cause the water to flow faster thru the pipe and lessen the scale buildup.

The water flows at about 3 gpm/20gallons per hour. I'm thinking that even 1/2" is big for this. Their logic was that a small amount of water flowing through a bigger pipe would allow the scale to build up even more. It would still break off, maybe in bigger chunks to still clog the pipe.

The flush idea is good and would be very easy to incorporate. Maybe I can even flush some mild acid to clean out the scale annually.

The pex intrigued me because it is super shiny inside and the mfg. really promote the no scale feature. Of course, they are trying to sell their product over copper.

Thanks everyone, and keep the "real world" advice coming.

 

[Jadnashua]

When used in a supply system where the pipe is full of water all the time, scale buildup would likely be lower with pex than others. But, not when used as a drain and you have air involved.

 

[Gary Slusser]

Gary, that was my very first idea also, but others told me just the opposite. They said that going to a smaller I.D. will cause the water to flow faster thru the pipe and lessen the scale buildup.

And yet hard water scale builds up faster the higher the velocity of the flow.

The water flows at about 3 gpm/20gallons per hour. I'm thinking that even 1/2" is big for this. Their logic was that a small amount of water flowing through a bigger pipe would allow the scale to build up even more. It would still break off, maybe in bigger chunks to still clog the pipe.

If the pipe didn't expand and contract due to temp changes, the scale wouldn't break off unless the pipe was compressed or moved somehow.

The flush idea is good and would be very easy to incorporate. Maybe I can even flush some mild acid to clean out the scale annually.

I'd go with 3/4' PE and if I could easily get an acid or CLR in the line by adding a stop valve to the far end of the pipe to let it soak maybe overnight, that's what I'd do every few months.

 

[Treeman]

Thank you for the ideas. The pipe gets buried when it goes outdoors, only about 6" deep, so there is lots of movement, I imagine. Not sure what I am going to do, but occasional cleaning will be part of the new routine.

And to correct my mistake, it flows at 0.3 gpm/20gph. (not 3 gpm).

 

[NHmaster3015]

This is a condensate drain line from evap coils so there is no volume or pressure to speak of. Clogging of condensate lines no matter what material they are made of is a common problem and on shorter runs we have special brushes that scrub it out. changing to pex will make zero difference, in fact, changing to anything probably will not make a difference because the scale precipitates out of the water as it flows along the pipe. Increasing the line size is a good idea because it will take longer to plug off than a smaller pipe. Either put in clean outs along the run or set the system up with a valve and a place to put a high pressure hose and flush it regularly. We have some industrial roof top units that have a similar arraingement so the maintenance guys can flush it out without having to call us. BTW, pex is no better at scale reduction than any other pipe. copper will form a "slime" on the inside that is every bit as slippery as the slippriest plastics.

 

[Treeman]

Thank you, Mr. Hays. This is an evaporative pad cooler similar, but different than "swamp coolers". The bleed line diverts a percentage of water out of the system to be replaced with fresh water to avoid excess mineral build up. But, I think that the scale precipitation is the same.....probably worse because the system turns off every night.

Thanks again for all the ideas. According to most of you, PEX is not the silver bullet to alleviate scale problems. Routine maintenance seems to be a common denominator.