Antifreeze installationinto a heating boiler Toxicity of Propylene Glycol
Anti-Freeze used in boilers, RVs, & other applications

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Properties of propylene glycol used as an RV or heating boiler antifreeze and in other applications.

This article series describes how to add anti-freeze to a heating boiler and to the hot water or hydronic heating system piping, baseboards, convectors, radiators, etc. to protect the system from freeze damage.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Propylene Glycol Properties, Toxicity, Poisoning Symptoms, Detection in Water

Input feed to a heating boiler riser pipe (C) Daniel FriedmanReader Question: How can you tell if the propylene glycol is leaking into the drinking water?

3 September 2015 AJ said:
How can you tell if the propylene glycol is leaking into the drinking water? What are the signs? Can it be seen, tasted or smelled?



First, if you're asking about leaks in a tankless coil in a heating boiler that has been treated with propylene glycol as an antifreeze solution, except when the building has lost water pressure, the leaks would tend to be in the opposite direction: from the tanklsess coil into the boiler, not the other way around.
See TANKLESS COIL / HOT WATER COIL LEAKS if that's your concern.

The U.S. ATSDR data on ingestion or respiration of propylene glycol at high levels enough to be discussed as toxic includes symptoms resembling inebreiation or "drunkeness" that we detail in a bulleted list below.

At very low concentrations you'd not know by taste (sweetness) that propylene glycol was in your drinking water. You'd need a water test lab assay test. The state of New Hampshire in the U.S. published comments including

There is no federal or state drinking water guideline for propylene glycol, and EPA has no approved oral or inhalation toxicity values for it. However, DES has determined that 30,000 ppb is an appropriate interim drinking water guideline for propylene glycol based on current toxicity
information and that there is also dietary exposure because of its use as a food additive.
- retrieved 3 Sept 2015 original source

Various uses of propylene glycol as an antifreeze in RVs, building heating systems, and other applications are discussed

Standardized test procedure for proplylene glycol

ASTM E202 - 12 Standard Test Methods for Analysis of Ethylene Glycols and Propylene Glycol - Quoting: These test methods measure certain chemical and physical properties of ethylene glycols and propylene glycols and may be used to determine compliance with specification in which limits are established for these properties. For those tests that use the procedure of another ASTM test method, that test method should be consulted for additional information on the significance and use of that test.

There are tests for propylene glycol both as medical tests (difficult as we cite below) and as a concentration in antifreeze solutions but I could not find an expert source citing a commonly-used test for low levels of propylene glycol in drinking water.

Indirectly and more crudely there are "antifreeze test strips" used in the automotive industry that will respond to both the toxic and the potable glycols. But I'm doubtful that such testing would be sufficiently sensitive to detect low levels of glycol in a building's water supply or well.

This ATSDR comment on proplyene glycol is helpful

Propylene glycol is generally considered to be a safe chemical, and is not routinely tested for, unless specific exposure, such as to a medicine or cosmetic, can be linked with the observed bad symptoms. Since propylene glycol breaks down very quickly in the body, it is very difficult to detect.
... According to the World Health Organization, the acceptable dietary intake of propylene glycol is 25 mg of propylene glycol for every kilogram (kg) of body weight.

The following describes how to identify propylene glycol but NOT how to detect it in low concentrations

Identification (1) To 1 ml of Propylene Glycol, add 0.5 g of potassium hydrogen sulfate, and heat. A fruity odor is evolved.

(2) With 2-3 drops of Propylene Glycol, mix 0.7 g triphenylchloromethane, add 1 ml of pyridine, heat with a reflux condenser on a water bath for an hour, and cool. Dissolve in 20 ml of acetone while heating, add 0.02 g of active carbon, stir, and filter. Concentrate the filtrate to about 10 ml, and cool. Collect the diposited crystals by filtration and dry for 4 hours in a desiccater. The melting point of the crystals so obtained is 174-178℃. - (2008). Health effects of ethylene glycol and propylene glycol. Retrieved from

Symptoms of Polypropylene Glycol Poisoning

Neurological Effects of Propylene Glycol if Consumed at Toxic Levels

Neurologic effects: The initial phase of ethylene glycol poisoning is characterized by inebriation caused by unmetabolized ethylene glycol. In acute poisoning cases, the following symptoms are common (Parry and Wallach 1974; Buell, Sterling et al. 1998)

The ATSDR article continues:

Possible sequelae of severe poisonings (Walder and Tyler 1994; Hantson, Vanbinst et al. 2002) include

The ATSDR document (cited below, includes discussion of cranial nerve damage and respiratory effects, renal effects, and other effects.

Reader Question: use of the Propylend Glycol that is put in RV's,Cabin systems,etc. (Uni-Gard-50) sold in Home Depot,

(Nov 16, 2012) Ron said:
Why can't the use of the Propylend Glycol that is put in RV's,Cabin systems,etc.(Uni-Gard-50) sold in Home Depot, be used in the Hot Water system of a home.



In the article above that is exactly what experts recommended.

Reader Question: oily look in boiler water after installing antifreeze

(Jan 23, 2014) Marni Olsen said:
My plumber recently drained my Weil McLain Boiler & I have a Sid Harvery McDonnell & Miller cut-off. He put in what I believe is anti-freeze the water color is a light green & when I drain the water its slightly oily looking. I need to know if this is toxic since I toss the water outside into the ground. Also is this the right anti freeze to use? THe plumber will not return calls & will not speak to me of what he did.


Marni, there are two different types of antifreeze used in heating systems, one toxic and the other using food-grade products is non-toxic. You will need to ask the installer what product was used.

Installers may use either propylene glycol (non-toxic food-grade antifreeze, recommended where a tankless coil is used on a heating boiler and in some other cases), or ethylene glycol (automotive type and highly toxic antifreeze).

Leave a polite message for your plumber noting that you just want to know the brand and product of antifreeze installed.

About your comment "when I drain the water" - I'm unclear why you would ever be draining water from your heating system - that's not a normal step except for steam boilers which surely is not your case. What's going on ?

Let us know what you are told and I can comment further.

Reader Question: other uses are there for boiler glycol

(Oct 5, 2014) Fred said:
What other uses are there for boiler glycol. I just changed boilers and have about 15 gallons left over


Food grade antifreeze products are also used in winterizing RVs and plumbing.

Propylene Glycol Toxicity Research

Heating boiler antifreeze, usually a non-toxic polypropylene glycol anti-freeze and water mixture is installed in hot water heating boilers and plumbing systems to reduce the risk of expensive freeze damage to the heating system piping and of course to avoid costly water or even mold contamination that occurs when an unattended building suffers burst heating piping and leaks.

Article Series Contents


Continue reading at ANTIFREEZE for BOILERS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Suggested citation for this web page

PROPYLENE GLYCOL DETECTION & POISONING SYMPTOMS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman