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Aqua-Hot Service Warning for DYI

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In older Aqua-Hot systems, DO NOT attempt to "tighten" the boiler bulkhead fittings in response to an antifreeze leak.

It is a real temptation, since a 7/8" crescent wrench can be laid against the stainless shroud and move what appears to be compression fittings. These are solder-on joints; the cause of dripping might be failure of the solder joint to begin with. Further movement can twist the boiler coil and restrict water passage while at the same time increasing the leak.

The price of a boiler overhaul on the older models is about $8,000!

I've put about ten manhours into removing our AHE-100-4S after noticing a persistent antifreeze leak. Rather than returning it to service with the obsolete bulkhead fittings, I upgraded to compression fittings at the bulkhead, re-soldered the original end fittings. Removed from the cabinet, the boiler can then be descaled, leak-tested. I also pressurized the hot water coil to ensure there was no leakage.

Having the boiler out is a good opportunity to replace hoses, install a new insulation blanket, put stainless hardware on the feet instead of the rust-prone steel pop rivets used at the factory. 

Following Aqua-Hot Service Manual instructions, I also soaked the mix valve in diluted CLR.

While applications differ, my coach needs about 10 gallons of antifreeze in addition to the 16 gallons held by the boiler.

In our case, this whole overhaul process was innocently begun with replacement of the electrical heater element. The element is just like your home version, down to the wrench size. To replace the element, the boiler must first be drained. I dumped the non-toxic antifreeze, bought 22 bottles of Camco concentrate on line for about $8 each. It is important to use distilled water; a supersize IV rig fashioned from a plastic jug and hung on a ladder is a good way to execute the refill. 

Tracing leaks on the boiler bulkhead is made difficult by the snug cowling/shroud that encloses these units. Q-tips are handy for determining which fitting is the culprit. If either of the water In/Out fittings are allowing antifreeze to escape, the sole remedy is boiler removal.

Did I mention that the cost of this is $8,000 plus shipping and taxes, if Aqua-Hot does the work?😏


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Andy, I would like to know, where did you get the $8,000 figure?  You can replace the unit with a upgrade to a 250D for $5895 or a 450DE for $9895..installed.

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