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I've read several Isotemp installs some say you need the G thread 1/2" female to NPT thread 1/2" male pipe fitting adapter or some version of the G thread to NPT thread adapter.

So if you have the Isotemp with thermostat mixer valve you need the G(BSP) adapter.

I asked and answered my question.
 

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Ok, I know that everyone is enduring sleepless nights waiting for my Loctite 592 update!! For your entertainment:

1) Applied 'minimal amount' of Loctite 592 to fittings, then waited an impatient 30 minutes and drove van up to temp to check for leaks. Of course both coolant lines at the water heater fittings were leaking...a lot!! ?

2) Panicked and asked everyone what went wrong! Lots of great feedback, thank you! (y) Also called Isotemp and Loctite for product use clarification.

3) Reinstalled all fittings with a "substantial amount" of 592 this time around. The Loctite literature was unclear as some pages stated 24 hour cure time, some said 72 hour cure time. So I wait.... :sleep:

4) It's been 72 hours and I check the fittings. By "check" I mean visually inspect them with no idea what I am looking at. Then I touch the excess 592 goop that squeezed out of the fittings when I installed them 3 days ago. It's still as wet as when it came out of the tube! :eek: How is this possible??? Not even slightly tacky or dried?!

5) Call Loctite again and got an awesome tech support guy who informed me that this Loctited product is anaerobic and will never dry outside of the fitting. It will, however, cure inside the fitting in around 24 hours. Of special note he asked if both metals of the fitting were "Active". Huh??? Turns out that the brass female fittings to the coolant lines are active, but the male stainless steel fittings of the water heater are inactive. The tech explained that if we had used the Loctite primer on the inactive metal our 592 sealant would likely have cured in about 24 hours. Without the primer the sealant would likely take 72-96 hours to cure. But it would indeed eventually cure based on some molecular explanation that confused me.

Bottom line: Use the primer (which I didn't... ugh), use lots of sealant, tighten fittings completely, allow product to cure.

I am going to give this sealant another couple of days to cure and will let everyone know if it leaks or not.
 

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I haven't tested it yet! I have been struggling with electrical this week! I am confident that the fittings will hold after talking to the Loctite tech support guy. But.... still a little paranoid! LOL Leak test this week, either tomorrow or Wed. (y)
 

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No leaks! Works perfect!!

This is all obvious stuff, but I am a slow learner!:
  • If you use the loctite, use lots of it!
  • Tighten the fittings!
  • Let it cure at least 4 days (unless you use the primer, than apparently only 24 hours cure time)
 

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I cut into both of them and essentially connected the isotemp in 'parallel' with the cab heater. That way the isotemp doesn't affect the cab heater output.
Won't it just take the path of least resistance? In other words, won't most of the flow or all of the flow just go through the heater core without making it back to the isotemp tank? At that point, I think maybe just a venturi effect even, creating some flow to the water heater? I plan to hook up in series, so that the pressure is the same in the system as a whole, cab heater should be first in my mind, since there should be more than enough heat at 190plus degrees. Thoughts?
 

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Parallel. If something goes wrong, you need to be able to isolate the lines without messing with the engines core colling function. It is how the factory kit is designed.

I'm sure more coolant flows through the core than takes the 30 foot round trip to my water heater, but I still get hot water in 30-45 minutes.
 

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Ditto. Mine also works great in parallel, just as it's designed to. Add ball valves at both tees so you can isolate the loop for repairs, etc. Adjusting one valve regulates coolant flow to the HW tank.
 

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Won't it just take the path of least resistance? In other words, won't most of the flow or all of the flow just go through the heater core without making it back to the isotemp tank? At that point, I think maybe just a venturi effect even, creating some flow to the water heater? I plan to hook up in series, so that the pressure is the same in the system as a whole, cab heater should be first in my mind, since there should be more than enough heat at 190plus degrees. Thoughts?
I'm not recommending either way, but series would work, in theory.
Seems like everyone hooks up in parallel and they get good heat exchange.
If you did hook up in series, I would recommend a 3rd valve. So you can close the loop to the water heater for repairs or so you're not heating water when not needed, open the center valve and it would operate as normal.
The downside is that it's a little more work and a few extra points of potential failure.
The idea would be along these lines.
KIMG0442.JPG
 

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Another thing to keep in mind is as Steve mentioned, in parallel, you can restrict the flow to the water heater without affecting the flow in the rest of the system.
In series, you would have to leave it wide open.
One reason the water heater manufacturer may recommend parallel is their heat exchange tubing inside the unit may restrict flow in the entire system if in series. Something to consider.
 

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Tricky. I saw that too. Do we each get a dollar? ;)
RnR's point about possible system restrictions in series brings up another point. Some of us have asked about warranty implications and have been assured that tapping into heater hoses for an aux (rear) heater is acceptable, as it should be since they provide parts for it. But what if parallel is considered the "industry standard" for aux heaters? I'll bet my dollar it is.
 

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At the end of the day, I think the standard hookup method (parallel) is the safest bet for the system to function as intended, with the least risk of failure or complications.
I'm sure the manufacturers went through all of this and tested several different ways to operate it and settled on the current standard.
 

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I would only attempt my theoretical setup if I could verify that the ID of the heat exchange tubes in the water heater, valves and extra length of hose did not restrict coolant flow in any amount.
Even if it didn't, the chance of human error in babysitting the valves could lead to serious issues and the only real advantage that I can think of is that it would heat the water a little faster.
So, again, I recommend just hooking it up the way the manufacturer says to.
 

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Great picture, RnR, That's exactly what I was thinking. I'm not sure what there is room for under the hood, but your valve arrangement to bypass the WH is a must in my mind. Obviously there is enough flow in the system so that many have had luck with just 3/8 hose on just a parallel connection. I have also seen comments about different supply and return line fitting sizes in a (heater kit?). Seems to me that these are all responsible in regulating how much flow a person wants to get through to the water heater heat-exchanger. The length of our hose runs will also vary flow. So people getting different heat up times at the tank makes sense to me. After the comments, I think I can go for parallel. But to be sure of a good flow, I'm going to stick with a slightly larger hose run to the tank in the rear of my 158", say the 5/8 or even the 3/4 based on how easy the hose will be to run through the floor and make the required corners that I want. I think that will give me the quickest heat up times. Actually, since the water is so hot, I'm kind of thinking that a set of 3/4" lines might just be overkill.
 

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has anyone considered using the "plate" type heat exchanger? I saw it being used in one of the "1-hour shower" tubes. here is a link to the webpage for the 50 plate heat exchanger. (don't know how to post a picture, sorry).
Happy Holidays to All!
 
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