Dielectric union and glycol

CBRob

What would be the correct union to use for supply and return on a boiler with glycol?
Is the galvanized part of a dielectric union going to react with glycol?

CBRob

On the subject of corrosion, 
I noticed that triangle tube requires a pH between 6 and 8 for their boilers.
It's hard to find an inhibitor or glycol below 8.
Seems like everyone else is saying a pH close to 6 is asking for trouble.

Intplm.

Beats me. I've used dielectric and none dielectric on many installations and just follow the directions provided by the manufacturer of the glycol. Works pretty well from there.

CBRob

Triangle tube sells a near boiler kit for the combi that uses dielectric unions, so I guess I'm good.
I've seen a union on the domestic water side corrode all to hell...
They don't seem to work as intended sometimes

hot_rod

I don't think it is a good idea to use galvanized fittings or pipe with glycol systems. According to Dow at least.

That being said the Weil Ultra boilers had, maybe still do, galvanized piping inside.

GroundUp

A few years back I got to replace nearly 1000 dielectric unions in a school running a glycol system, only 3 years old and more than half of them were already leaking. Dielectric unions (or galvanized anything, for that matter) don't belong anywhere near any hydronic system IMO, glycol or not. First of all the whole electrolysis theory is completely nonexistent in a leak free hydronic system so "dielectric" of any sort is unnecessary. Secondly, dielectric unions need a very distinct torque to prevent squeezing out the gasket and creating a leak which is almost always overtightened- and the galvanic corrosion that comes with galvanized anything is less than ideal. Third, if electrolysis is for some reason a concern, brass acts as a dielectric between steel and copper. Whether a valve or union, even a brass nipple, electrolysis isn't happening.

Do yourself a favor and skip the dielectric unions

CBRob

weird...
Huh?
 
Triangle tube also requires a pH between 6 and 8.
Hard to find glycol or inhibitors in that range.

@Derheatmeister

When looking for deionized water, 
Is distilled water a decent substitute?

What about using RO filtered water? 

jumper

Hope we're not talking about galvanized inside?
Hot water dissolves zinc oxide
Glycol makes zinc flake off.
Glycol for hydronics is supposed to contain corrosion inhibitors.
Supposed to send sample annually to check if you need more inhibitor.
At least that is what remember DOW informing me thirty years ago.

Canucker

CBRob said:

weird...
Huh?
 
Triangle tube also requires a pH between 6 and 8.
Hard to find glycol or inhibitors in that range.

@Derheatmeister

When looking for deionized water, 
Is distilled water a decent substitute?

What about using RO filtered water? 

If I'm remembering my chemistry, for your application they should be functionally the same. I believe the difference with distilled water is that it also has organic impurities removed as well. Unless you plan on drinking it, you can use either.

CBRob

Another question about doing a complete job of replacing old glycol/system water.

step 1 clean out system and flush with city water.
step 2 ??? how do you replace the clean city water in the system with distilled or deionized? add a dye to it?
or blow it out like a sprinkler system before refilling.
Step 3 Refill with distilled water ( with inhibitor?) and PH to 8 or number that is within manufacturer specs?

mattmia2

Deionized water still has dissolved carbon dioxide, Distilled water has the carbon dioxide driven off.

CBRob

Does a ppm reading from a cheap conductivity meter give a decent idea of hardness,?
My town uses hi altitude creek water and shows 37 ppm out of the tap.

hot_rod

You are reading the conductivity with that meter, to check hardness in GPG grains per gallon, you need a hardness test kit. Fairly inexpensive on Amazon.
The minerals in the water that cause scaling are related to the hardness.
\
The conductivity is an indication of how well the fluid can support electrolysis.

ALL metals can set up some electrolysis, even brand new copper connected to old copper, according to the CDA. Keeping conductivity low will help eliminate the potential.

Keep in mind if you use probe type low water cutoff devices you need at some conductivity in the water, around 10 ppm or more.

Distilling, RO and deionizing are all methods of getting near pure water, just with different methods. For small systems DI, resin based, is usually the easiest, most affordable. When talking thousands of gallons RO starts to be more common as the membranes can be repurposes. Car washes often RO the final rinse water to eliminate spotting.

With DI once the resin is plugged it needs to be replaced.

dopey27177

One thing I remember from my classes on hydronic heating at the the LITTLE RED SCHOOL HOUSE was Dielectrics fittings on water heating systems is not needed. Using the same materials thru out the system tends to keep hydrolysis and electrolysis down to almost a non existent occurrence. Additionally the boiler and all piping is attached to the domestic water piping. Domestic water piping is grounded so all the heating piping and boiler is also grounded and this by itself helps prevent hydrolysis and electrolysis from occurring.

Jake

Canucker

mattmia2 said:

Deionized water still has dissolved carbon dioxide, Distilled water has the carbon dioxide driven off.

I agree but unless it's sealed up quickly that condition doesn't last long

mattmia2

Canucker said:

mattmia2 said:

Deionized water still has dissolved carbon dioxide, Distilled water has the carbon dioxide driven off.

I agree but unless it's sealed up quickly that condition doesn't last long

in a sealed system with air elimination there isn't much difference. If you are doing chemical analysis where ph is important the difference is important.

Canucker

mattmia2 said:

Canucker said:

mattmia2 said:

Deionized water still has dissolved carbon dioxide, Distilled water has the carbon dioxide driven off.

I agree but unless it's sealed up quickly that condition doesn't last long

in a sealed system with air elimination there isn't much difference. If you are doing chemical analysis where ph is important the difference is important.

Well aware of that, thanks. How do propose keeping the CO2 out of the liquid while it cools or while it gets loaded into the system? Either water would be more than good enough. Buffer it in the drum and load up the system, it's not worth the hair splitting to distinguish them for this application