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I've read that ethylene glycol is better for the soft parts...

1K views 5 replies 3 participants last post by  pdqaltair 
#1 ·
... Hoses, elastomers, joker valves, and flappers. That is one of the reasons EG is used in cars instead of propylene glycol; it's a little easier on the hoses and seals.

So what's wrong with using automotive engine coolant in the head?
* Engine coolant is cheaper, when you consider that -50 PG has about the same freeze point and burst point as 20% EG (divide the $14/gal price by 5)?
* I don't care that it's not potable, since no one is likely to drink from the blackwater tank.
* It is just as biodegradable as PG.
* Both have equivalent toxicity to fish and marine life. Look a the MSDSs.
* All chemical compatibility tables show EG as an "A" and PG as a "C".
* In the spring, by the time you flush it into the waste tank and let it sit for a few weeks, it will mostly biodegrade before it even gets to the sewer.

Seems like a bad habit more than good engineering. But please, offer reasoning.

The potable systems absolutely need to use PG, for safety reasons._____________

Sail Delmarva: Search results for antifreeze
 
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#2 ·
Probably a bad habit of engineering I would think. But then again, there are differences between the advice given from a "public health" perspective and the advice your doctor gives YOU which is IN context.

I think that the great unwashed masses (or recently washed with full greywater tanks) who own RVs are quite likely to confuse one type with another, or one inlet with another. That might be part of the reason. Another part of the reason is that the city water people might not want antifreeze in the city sewer system. Technically you are supposed to dispose of engine antifreeze at a household hazmat site.

Where is Gary H. Lucas when you need him?

Here is a little of what google says on the subject. Sorry, no engineering white papers came up.

1: What should I do with used antifreeze that I remove from my radiator? Can I just pour it down the drain or the sewer in the street?

Never pour used antifreeze down the drain or in the street. Both ethylene glycol and propylene glycol are toxic. Used antifreeze also picks up heavy metals like lead during use in the engine. These should not be released to the environment. Properly dispose of used antifreeze at an appropriate collection center.


2: Antifreeze has a sweet taste that can attract pets and small children. So do not pour antifreeze on the ground outdoors and do not put it in the garbage. Also, never dump antifreeze down a household drain or toilet if you have a septic system. If you're connected to a municipal sewage plant, check before dumping antifreeze down a drain or toilet.

3: It won't hurt the treatment plant. DDawg16 is assuming the anti-freeze cannot be treated, and will remain in it's "toxic" form. Well, it is treated, and completely. Anti-freeze is nothing more than a glycol based fluid, whether it's propylene or ethylene (others are also common), and it actually acts like a food source to treatment plants (like alcohol or sugar). I'm not condoning dumping it in huge numbers, but 5 gallons isn't going to hurt it. Want to know what's REALLY toxic to treatment plants? Milk. Yep, regular, plain old milk. Too much and it'll shock the system (depending , overload it, and it'll kill all the biomass if the plant is small enough (especially under 20,000 GPD or a town of 200 people).

Now, don't get me wrong, I am not encouraging you to dump the anti-freeze down the drain. In fact, the best place to take it is a car dealership, as they routinely have someone come by and filter it (usually on-site, a friend of mine does this full time), so it's reused, and they'll make a profit from it. Therefore you SHOULD NOT pay them to take it, most places I have seen will accept it willingly, for the aforementioned reason.

DO NOT MIX IT WITH OIL! This does nothing but screw up the oil, and it creates a substance that is much harder to get rid of than either component separately.

BTW, I am licensed in treating water, wastewater, and groundwater sites (Superfund), and have worked in the industry for over 10 years. I have 8 different licenses in the field, all top grade.


MedSailor
 
#4 ·
If you read the links, inside the link that I posted, there are scholarly articles regarding relative toxicity. As for the "general public" statement, I certainly agree. Those that can't keep their chemicals straight, please disregard this thread and buy pink potable water antifreeze.

1. We're not talking about used antifreeze, the metals toxicity angle is mute. Since neither PG or EG mixed with blackwater, the recycling alternative is mute.

2. It don't taste sweet once in the backwater system. First, it is not available to pets or children, and second I doubt they would touch it.

3. Even sugar and syrups from bottling plant, released in large amounts, have cause some major upsets. In this case, we are taking about 1/2 pint of EG in 1/2 gallon of water.

4. I built the east coast's largest glycol recycling plant some 20 years ago. The glycol and water are distilled away from the old additives and residue and virgin quality grade EG is produced. I've never been clear on how a portable truck unit (no laboratory) can filter used stuff that has not been tested and return it to the dealer without batch testing, and be certain of what has been accomplished. Such products are generally highly variable--depending on what cars have been serviced and what the mechanic poured in the tank--and do not meet all ASTM and OEM requirements; there is a secondary lesser standard for antifreeze recycled on-site, presumably for use in older cars. Chemistry is not so simple. But since this will not be recycled this is off the point.

Winterization antifreeze in general is NOT recyclable. On-site recyclers can only process material that is automotive type to begin with and it MUST be >45% EG. Distillers can be more forgiving (more complex process) but they still have no interest in material that is more than 2/3 water, and most potable water AF has 75% water in it as purchased, plus whatever water was in the system.

And some joker is ALWAYS going to pick on ambiguous wording. Ouch. Actually, PG is generally used in those "soft part" fluids, and obviously NOT EG.
 
#5 ·
$14 a gallon? The pink stuff should be about $3-4 a gallon before any sales or discounts.

Y'all experts are gonna tell me now that all the lables and claims that the pink stuff is less toxic or non-toxic are lies? Or just that the new engine AFs have finally caught up with that aspect of them?

I have to admit, when I'm looking for engine AF I'm looking at "permanent" and additives and metal compatibility, and don't care about toxicity. But really, the pink stuff? Should be about 1/4 the cost last I checked, unless I'm not accounting for dilutions properly.
 
#6 ·
Quote: $14 a gallon? The pink stuff should be about $3-4 a gallon before any sales or discounts.
Re: Read more closely; concentrate EG at $14/gallon divided by 5 is $2.80 per gallon when providing equivalent protection to PG, before any discounts.

Quote: Y'all experts are gonna tell me now that all the labels and claims that the pink stuff is less toxic or non-toxic are lies? Or just that the new engine AFs have finally caught up with that aspect of them?
Re: Read more closely. EG has equivalent toxicity to marine life as PG. I quoted other sources. PG is less toxic to mammals, but fish are not mammals. For example, zinc is deadly to marine life, but people take zinc pills. Dog should not be fed chocolate. I could go on, but I think the point is clear. The labels are completely truthful when it comes to potable applications, but this is not relevant for blackwater or engines.

And no, engine antifreeze has not changed in this regard and is not headed in that dirrection. Many states now require a bitterant to be added to engine coolant in retail packaging, but the toxicity is not reduced.

I would be very interested in any scholarly work on EG vs PG marine toxicity and biodegradability, from a source with no dog in the fight. I posted this link before:

Abstract from 1996 SRA-Europe Annual Meeting
 
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