Changing out the Alde fluid.

Thanks @ScottG, I feel the same way and am sorry for continuing the brain drain. We can problem solve on the side! I will forward coherent thoughts as available by PM. 

@ScottG and @tybladesmith, I confirmed what you already knew, the drain tee is off the reservoir to ALDE cold inlet.  I also did consider using a drill-powered pump, as mentioned real early in this thread.  I'm concerned that the lubrication that is shipped with the pump could contaminate the glycol solution.  For grins I ran a new drill pump in a washtub with a bunch of water.  After doing that for a few gallons, there was still grease in the drill pump.  I suppose it's needed to make the pump last, but might leave some contamination within the Alde fluid.  I suspect that most harbor Freight transfer pumps in the $60-100 range might have the same contamination issues.  I think that I'm back to trying the following:   
1) Use a sureflo pump (or pumps), like the Alde system
2) Remove the Alde drain and drain what you can.  Replace the drain
3) Add a drain tee in the line between the radiator and the reservoir. 
4) Open that drain and push new fluid in through the reservoir outlet.  I think some types of toilet fill pipes have a half-round rubber washer with flange that would create a sufficient seal on the outlet pipe, inside the reservoir.
5) Once fluid is changed, close the drain tee.  Fill the reservoir, then draw from the reservoir and pump through the same pipe to the reservoir outlet.  That should bleed the system.  (The only question might be is one sureflow pump or do we need 2, like the Alde tool?)
 

In all this is sounding like a big project.  I may not want to attempt this a week before cold-weather camping!

Hey @ScottG, I've enjoyed catching up on these old discussions of a topic in search of the elusive definitive answers about replacing glycol, and all the great recent contributions as well as your nice diagrams. 

Your last comment about pumping glycol "in the proper direction" made me wonder whether you meant the chosen direction for a particular method, or that there is only one direction that can work (e.g., the normal direction of flow for the built-in circulation pump)?  I was under the impression that when the built-in pump is not in use, that it should allow flow in either direction; otherwise, the Alde glycol would not drain out as it apparently does when the low-point drain plug is removed.

I ask, because I have been contemplating a possible pump-less method of draining & filling glycol in the opposite direction of the normal circulation.  To illustrate, I've borrowed one of your nice diagrams (hope you don't mind) to show what I'm considering as a possible solution by using compressed air applied to the expansion tank to empty the system (& possibly to fill it at least partially)..

UPDATE (2-28-20):  THIS IDEA WILL NOT WORK due to a one-way valve inside the Alde output pipe that prevents backflow (see my later message)..

After opening the drain plug to drain by gravity about a gallon (minus the glycol in the loop of convector pipes), then clamping off both the hose between drain & expansion tank, as well as the overflow drain tube, then compressed air could be applied to the tank's air vent tube in order to push out the remaining glycol in the convector pipes.  I have calculated (see blue area) an estimate of the volume of these pipes (about a gallon) by measuring the length of the pipe route & doubling that since it's a loop.  I've read that the convector pipes have a 22mm diameter (or about 7/8").

The above procedure might allow the complete removal of old glycol, as desired, and should not require very much pressure. By comparison, even a 28" tall column of water exerts a pressure of only one psi.  I should also say that I have not tried this yet, but until I can, I'm offering up the idea to see what others may think.  So far, I've only seen one mention of trying air pressure at the tank, but  clamping of the open tubes wasn't stated, though it would be necessary for this to work.

As for filling the system, that may be another story.  I'm thinking that the convector tubes could be filled in the same manner, by adding glycol to the tank & pushing it through the convector tubes until it starts coming out of the open drain.  Then close the drain, remove clamps, add more glycol to the tank, and turn on the pump.  After that, I'm not sure the front half inside the Alde could be easily filled without trapping air inside the Alde.  Although the automatic bleeder is at the top of the Alde, I'd be worried about whether this could work.  So, filling might need to be done in a more conventional manner.

In any case, here are some photos, showing the location of the narrow overflow tube (a hemostat might work nicely for clamping this tube, and it could be clamped near the floor where it's easy to reach), and the similar air vent tube..


The air vent tube can be easily slipped out of its holder & the end brought over to where it can be easily reached.

Below is a similar tube with a barbed adapter that could be used for applying compressed air using a rubber-tipped blower type handle on the air hose.  If or when I do this, I would likely try less than 10psi on the pressure regulator at first.

Again, none of the above has been tested, but it's probably what I will do when the time comes, at least for emptying the old glycol.  I still need to test our glycol with my pH meter & refractometer.

Filling from the bottom with a hand pump, possibly with judicious use of a clamp, seems like it may be the ideal way to aim for, or else just pumping or pouring into the tank.  I also wonder if there is a type of drain fitting that would facilitate connecting the hose from a hand pump to the drain, for filling from the low point.

Thanks, @ScottG, for your reply. 
That's what I thought you meant, and your main concern seems to be about glycol flowing "backwards" through the pump.  However, here are a few points that might allay these concerns..

First, many have drained their glycol by simply removing the drain plug & collected a gallon or more of glycol, which we can presume comes mostly from the Alde "jacket" (I believe the specs say it holds 0.92G), plus what's in the expansion tank & its line to the drain.  So, if most of this flows by gravity through the pump to the drain, then there cannot be much, if any, resistance to reverse flow of glycol through the pump (at least at low pressure). 

Second, the reverse flow of draining the Alde glycol is indeed low pressure, because a column of liquid at only about a foot tall does not exert much.  12 inches of water, for example (about the height of the Alde), exerts only 0.43 psi at the bottom of the column (or 0.44 psi for glycol with a specific gravity of 1.026).  Using only 1 or 2 psi of compressed air should be enough to push & lift glycol out of the heating loop & into the Alde to drain, while not posing any risk to the pump, however, more pressure may be needed to actually blow it all out if the water column collapses under gravity in a larger diameter tube.  Using distilled water to displace the glycol may be required initially.

Third, there is at least one Alde circulation pump model I've seen where the brochure specifically states that "motor does not restrict circulation when not in use".  I would conclude this is also true for our model on the 3010, if it can freely drain the tank when the pump is off (reverse flow).  Circulation pumps are often built like a paddle wheel that has fan blades spinning in the liquid pushing it through the tube.  If at rest, fluid could still circulate between the blades, such as by gravity.

UPDATE (2-28-20):  THIS IDEA WILL NOT WORK due to a one-way valve inside the Alde output pipe that prevents backflow (see my later message)..
As for pushing glycol from the heating loop hoses back through the Alde to drain, unless Alde has some sort of check valves (I haven't heard of any), there should be no reason not to do this, as the glycol itself is all the same, because it normally circulates through the entire system.  As long as minimal pressure is used, I see no reason for concern.   IT DOES HAVE A CHECK VALVE.

The last thing I would want to do is disconnect a glycol hose inside the trailer if I can avoid it and any potential spill.  I also can't see trying to disconnect the expansion tank if that can be avoided.  I'd be curious to know what kind of psi levels are generated inside the system when using Alde's expensive service pump - I bet it's significantly more than a couple psi.  The circulating pump itself shouldn't need to generate more than 1-2 psi just to move glycol through the system.

I think your idea for adding a filling port valve near the drain tee is a good one, or else just adding a temporary barbed valve stopcock into the drain (secured with a hose clamp) for pumping in fresh glycol slowly from the outside with a hand pump. 
Or even just one of these, or a brass one..

Agree, @ScottG, and neither am I planning on doing anything soon, but winter is a good time for thinking & planning.  I may even wait another year if pH & specific gravity check out ok.  We've only had 2-1/2 camping seasons so far since buying our T@B new in Aug 2017.

After my most recent drain and fill, I'm happy to report that it's never been quieter.  No gurgling at all, I did the raise and lower tongue dance and the auto bleeder did the rest.

I really expect my once a year half replacements to keep the Alde protected.

Oui, yes, it is what Alde lists as a “non-return valve” which is the check valve you asked for it’s location on the system.

ScottG, de rien.

@Denny16, which T@B model has the extra red flow tank & pump?  I haven't seen this before.

Part 2 – Actually flushing and changing the fluid

Part 1 had the special tool creation.  This is what I did to change my Alde fluid.  It worked well with very little mess

Overview

Previous discussions seemed to talk a bunch about draining all the fluid out with the possibility of using compressed air, removing hoses, air in the system, risk of breakage, etc.  I set out to minimize the work, yet get a clean fluid change.  Basically, I just pushed the old fluid out with new fluid.  The amount of air introduced in the system was very minimal.  I did not disconnect ANY fittings or drain plugs. 

Items needed:

·    Special items, covered in section 1:

           o   Adapters to go within Alde reserve tank (one straight, one with offset)

           o   Electric pump (used a good-quality RV water pump)

           o   Hoses to the pump (2)

           o   8-foot ½” OD vinyl tubing with hose end

·   Other items needed

           o   Flashlight

           o   2 gallons of Alde fluid.

                 (I used about 2-1/2 gallons but I wanted to flush out everything)

           o   Drill-powered pump “el-cheapo”

           o   Drill (to run the cheap pump)

           o   Standard short garden hose (8-feet should be enough)

           o   5-gallon bucket

 

Drain the excess fluid from the reservoir.  I put the 8-feet of vinyl tubing INTO the reservoir inlet hose and slid the hose down the inside of the hose.  I then inhaled to get most of the hose primed, attached the drill pump and pumped out the reservoir and the hose contents.  Remove the hose when completed.

(Some previous discussion talked about using the drain plug under the trailer.  Some said that it only cleans out the hose and not much really comes out of the Alde system.  So I figured, why even use the drain?  I just removed the fluid from the hose and reservoir.)

Attach the straight adapter to the standard garden hose.  Put the other end of the hose in the bucket.  Keep the adapter end near you for later.

Attach the pump inlet hose to the new bottle of fluid.   Attach the pump outlet to the offset adapter.  Hold the offset adapter in the bucket and briefly run the pump.  This will prime the pump and remove any crud/lubricant from the pump.  This will also remove all air from the new incoming fluid.

Insert the offset adapter in the Alde reservoir.  The neoprene end should fit in the reservoir outlet.  Now you insert the straight adapter to the reservoir inlet. It should be pretty easy to apply gentle pressure to both the adapters within the Alde reservoir to make a good seal.

SHOWTIME!

(It is advisable to have an assistant to help if something goes wrong.  Mine checked the outflow to the bucket and passed the new bottles of fluid to me.)

Turn on the pump, while holding the adapters within the Alde reservoir.   You should see the new fluid bottle drain and old fluid go to the bucket.  It takes about 15-20 seconds to drain a 1-gallon bottle with a 3 GPM pump.  Stop the pump before the bottle gets totally empty.  That way you won’t introduce air in the system.  I put in about 2 gallons of fluid in the system.  The fluid to the bucket was pretty clear, so I pumped about another ½ gallon just to be sure I got rid of the old fluid.

The theory of having the inlet and outlet adapters sealed to the reservoir was that no fluid would leak in the reservoir, thus it would stay empty.  That worked for me.  If you did get some leakage, you may need to get the drill pump and hose and remove leaked fluid from the reservoir.

Remove the straight adapter from the Alde reservoir.  Add new fluid to the reservoir.  (I did a little above “Max”.)  Leave the offset adapter in the reservoir.

Remove the pump inlet hose from the new fluid bottle and place inside and to the bottom of the Alde reservoir.

Ensure the offset adapter is held in the reservoir outlet and the pump inlet hose is below the fluid level.  Run the pump about 10 minutes to purge any air from the system.  I had a few spurts, but it appeared that I did not have any air in my system.

(The Alde tool uses 2 pumps working in parallel, to really pump the water fast.  My one pump seemed to be enough.)

Remove all your tubing, pumps etc.  To be sure, I ran the Alde circulator pump about another 10 minutes, then I turned on the heat and checked for operation.  All seems good.

Let me know your thoughts.  If someone wants to borrow this setup please let me know.  I live in Lexington, KY. 

Picture 1 shows the fluid being filled and the old being forced out.  The new fluid is the bottle on the left.  The pump inlet is on the right pump side.  The old fluid is exiting diagonally, out the bottom right corner of the picture.

Picture 2 is a view of the fluid being drained. 


Picture 3 shows the pump circulating fluid to purge any air.



Picture 4 is the setup used to do the initial drain from the reservoir and the inlet hose. (and my left foot)