Watermaker Pickling

[nhschneider]

I hope there's a chemist out there that can answer this question.

In preparation recently for a 'certain medical procedure' (I'll not-so-delicately decline to say which one), I was required to drink a large quantity of Miralax, which I discovered is Polyethylene Glycol. Remembering instructions for winterizing my watermaker, I initially thought this was the same chemical Spectra recommends - many cruisers also recommend winterizing a watermaker instead of pickling it. Upon a closer look, Spectra recommends Propylene Glycol. After a little bit of research, I find that Propylene Glycol is not a biocide of any sort but does have a very low freezing point. Polyethylene Glycol has a higher freezing point but, other than that, seems to have many of the same applications as propylene glycol. Since I'm in the tropics and have little concern about protecting my watermaker from freezing, is there a reason why I couldn't use polyethylene glycol as a pickling agent? One of the aspects that I like about polyethylene glycol is that it's available in a relatively low-cost powder whereas the propylene glycol I can only find in a liquid form.

I think it's clear that Spectra's instructions for winterizing with propylene glycol is merely an effort to displace the sea water that's in the membranes and Clark pump. Does anyone have any thoughts on the matter?

Fair winds and calm seas.

[transmitterdan]

Propylene glycol is not poison. Ethylene glycol is a deadly poison. It is car antifreeze. If you drink it you will be very sick or die. Don't put ethylene glycol in your watermaker.

In the potion you drank they use food grade propylene glycol in place of water because it will not freeze during shipping. Propylene glycol is in many medicines and other products for the same reason. The stuff you drank probably had some other component in addition to propylene glycol that served the intended purpose.

Dan

[nhschneider]

Dan-
Good point and I agree about your comments regarding ethylene glycol. However, my question was about polyethylene glycol which is available over-the-counter under a variety of names, one of the more popular is Miralax. As you might have guessed, it's a laxative and it is not a poison. Polyethylene glycol is used in quite a few foods, cosmetics and medications.

My interest in it is that I would prefer to use something like polyethylene glycol to pickle my water maker as it isn't toxic.

[DSDman]

Better make sure the head is working good once you start drinking the water again!

[senormechanico]

I've owned my current boat equipped with a Spectra 180 for 17 years (in the PNW) and have never used biocide of any kind. I just pickle it with product water.
Product water "pickling" has lasted every year for over 6 months with no ill effects.
We recently returned from a month's vacation in Canada and used the watermaker for our H20 needs for the entire trip.

It has made good quality water made to spec or greater (under 200 and as low as 120 ppm and at rated gpd or better ) for the entire time of ownership.