I have had my fair share of Aqua Hot leaks and I thought that we might post the repairs along with the parts used to help others that may face a similar leak issue. As these systems age there are likely to be leaking issues to deal with by most of us. There certainly are some weak design points in these systems. This post will deal with a leaking filler neck.
The Aqua Hot design used a steel boiler that has a 1.5" OD steel tube welded to the boiler as a filler tube. A brass radiator cap receiver was then set on top and soldered to the steel pipe. There is no sleeve on the brass cap receiver that fits over the steel pipe so it is basically a very small surface area butted joint using dissimilar metals with lots of heating and cooling cycles. If you are lucky yours will hold up for the life of the unit. In my case my unit leaked when I bought the coach and the repair is to buy a new receiver, clean, flux, and solder it onto the steel pipe. I did that repair and it lasted about a year and with pressure the antifreeze began to weep between the steel pipe and solder interface. A solder joint is not a robust means of sealing a steel to brass interface especially when no sleeve is involved.
I had heard of a repair being made using clamps and hose so I headed in that direction given the poor current design of this joint. I purchased a billet aluminum weldable cap receiver (Canton Racing 80-092), a 1.5 inch OD x 4 inch aluminum pipe normally used for a turbo pipe install (CX Racing PIP 150-S-4), 4 inches of silicone 1.5 inch ID radiator hose from a local supply shop, Rotor Clip constant tension clamps (CTB-47 ST-FK 47mmm OD x 15MM). These clamps were not stocked in small quantities but Rotor Clip will send you a small quantity as a sample if you cannot find them at a supplier.
The repair consists of shielding the zone hoses with foil, drain one or two gallons of antifreeze from the system, unsolder the receiver, wipe away excess molten solder with a damp rag, seal the open pipe with a rag, crocus cloth the steel pipe stem until smooth, then wipe with solvent. At this point the boiler prep is done.
Cut the aluminum pipe to a length that will accommodate the clamp width above the "bugle" while also leaving room for a weld bead. Have the pipe welded to the cap receiver. On one hose clamp I had to remove about half of the clamp ears with a dremel tool to allow it to slide down within the stainless cabinet opening around the filler neck. I worked the hose and a clamp down over the steel filler tube and then pushed the cap receiver with the pipe into the hose and brought the second clamp up over it and released it. Couple the hose that goes to the expansion tank and clamp it. Fill the boiler and test it. Mine is leak free for a change. Not everyone will be comfortable with doing this job but if you get this leak you have a choice in how this job gets done for your repair. In both of my repairs I avoided having to pull the Aqua Hot and I believe the latest repair to be far superior method of sealing this problem area of the original design. Hopefully you will never have to deal with this....Hope this helps if you do. In one of my photos there is a stainless clamp that I did not use, I opted for the Rotor Clip clamp design.
Later Ed
