Best Of

Once it is done it will never be exposed to your home, the lining will be inside the pipe and will vent to the outside with the sewer vent system.

It is probably all the minerals in the water that have collected in there. I would use a good amount of citric or hydrochloric acid to re-dissolve them then flush it out. If there is significant sediment on the bottom which there could be several inches or more, you would have to break it up and suck it out. There is equipment to do this for commercial tanks but it could cost more than an new tank.

Make sure there is no steel piping from the tank. A single steel dielectric union can make a big slug of rusty water it is sitting for a while.

This is a tough problem. The inner tank wall is corrugated so there’s plenty of surface area there in addition to what might be a lot of sediment on the bottom. It sounds like you’re doing a good job flushing. I’d follow the manufacturer’s advice or replace the tank. What’s your water quality like? Is it high in iron? What happens if you use it everyday in a normal way? It might eventually clear up and be fine. This sediment is probably in all the piping too.

As Ed mentioned that may be a tank in tank design. The inner tank is stainless. Not many connections into that tank to add an anode?

Hi, If you could prevent further rusting, than flushing would likely be sufficient to give you clear water. If there is a way to install a powered anode, that would stop the rusting. I'd also make sure the water has little or no salt in it.

Yours, Larry

I doubt it is worth the effort to attempt any sort of cleaning. From what you described the integrity of the tank itself has been compromised and it is probably not going to last much longer.

This is like trying to buff and wax a car with a rotten frame.

A wet vac with a long skinny wand

From what I remember about that Triangle Tube tank, there are no access openings for cleaning. There is an inner Stainless Steel tank that is filled with potable water and an outer tank that has the boiler water in it. (no heat exchanger coil).  The only access to the inner tank is through the ¾” male, hot and cold water openings that are welded to the inner tank and welded through the outer tank. Not much space for a spray wash nozzle at a 90° angle to fit in those openings. The cold inlet has a plastic dip tube that runs to about 4" from the bottom. So no real access through that opening.

Since that tank is over 30 years old, you may want to think about replacing that indirect with something compatible with your new future system.

The center opening is for a vent to purge Boiler Water from the top of the tank. No potable water access there.