Alde hot water tank draining from the cold line?

TresK3

We have a 2019 Tab 400, and we're winding up our winter trip at Big Lagoon State Park, near Pensacola, Florida then heading back north.  To prepare for the freezing weather, I blew out all the water lines this afternoon (well, to prepare the trailer for the cold; I'm not sure we are prepared...).

To do this, I disconnected from city water, opened all the faucets, then opened the two low point drains. Maybe a gallon of water came out of the cold side, and very little from the hot low point.  Next I opened the yellow handled Alde drains; one on the blue line (cold water into the heater?) and one on the red line (hot water out?).  Basically, nothing came out of either - maybe a pint from the hot line, which worried me.  I left the drains open and raised the tongue to move any residual water to the back.  Still no more water from the Alde system.  After that, I closed all the drains, connected an air compressor to the city water inlet and pumped it up to about 30 PSI.  I opened each faucet, one at a time, and blew out the water in the lines.  I did two complete "circuits" of the trailer, to make certain they were good and clear.

Finally, I went back and opened all the drains again, just to let any last water out.  At this point, I started getting hot water coming out of the blue (cold?) Alde valve.  I'm not sure how much came out, because I couldn't get a bucket under the trailer to catch it, but it ran for several minutes - I would guess two gallons.

So... why didn't the Alde system drain the first time I opened the valve, and why did it come out of the blue line in the end?

Sharon_is_SAM

@TresK3 - not sure if you have seen “Winterizing 102” under the Category “User Manuals.../ Winterizing”, but, I list the steps differently.  

I noted early on that the Alde tank drained better when the system is pressurized, so we drain the tank before draining the remainder of the plumbing.  We drain the tank using the Safety/Relief valve.  The valve is on the cold water line closest to the Alde, then the cold water drain is further away from the Alde.  I always looked at the hot and cold water low point drains as a way to drain the lines - not the Alde tank.  

If there is any kind of a vacuum, the tank won’t drain.  

Denny16

The two yellow handled safety pressure relief/drain valves, one in blue line (fresh cold water into the Flo), the second on red line, heated water from the Flo to the Alde heater.  You drain the tanks from their respective water inout lines, which are connected at the lower part of the hot water tanks.  Heated water is forced out by pressure from the output side of the tanks.

I drain the hot water tank first (or in your case both hot water tanks, Flo and Alde) after disconnecting city water, and pumps off.  Remaining pressure in system will bleed off from Flo drain, then open the low point drains (with the sink faucet open (cold water setting) and shower valve set to hot water while draining the Alde tanks.  Then switch the two, sink on hot water setting, shower in cold.  Do not forget to drain the outside shower and toilet water lines (hold down the toilet flush lever).

Air pressure blow out also helps clear any remaining water, but even s small amount of water left in the pipes will not cause any damage.  I leave the sink faucet valve open, so any expansion in the pipes has a air pressure release point, to prevent any pipe expansion.

Cheers