Clean indirect using tankless descaler?

sunlight33

I have a 50-gal indirect water tank, can I use descaler made for tankless water heater to clean the inside? Basically I will drain the tank to half full (since the heating coil is in the bottom half of the tank), pour the descaler in and let it sit for an hour or two. What do you think?
Edit: Or I can dump a 2-pound bag of citric acid into the tank, is that going to achieve the same result?

Big Ed_4

What make indirect ? What is the issue ?

sunlight33

Just want to clean heating coil inside to make better heat transfer, tank is Viessmann.

heathead

Does the tank have a port clean out. What is the tank made of. If you have a port, open it up and pressure wash the inside and read the Viessmann directions for cleaning. If it is a stainless steel tank do not use any metal brushes, plastic only. Pulling the port will let you see what is going on inside and how much build up. Not much room to work but gives some idea of build up, What model tank do you have? Have you looked for directions for cleaning from Viessmann's web site.

sunlight33

Viessmann recommended pressure wash and chemical cleaner (no muriatic acid) . Mine doesn't have the port (only 79-gal and above units have them) so can I do it only using citric acid?

sunlight33

My original question was for product like this one: https://www.supplyhouse.com/Qwik-Products-QT7710-Qwik-Descaler-1-Gallon

bucksnort

I would think that you just can't dump a descaler in a tank and expect it to work effectively. Wouldn't it be better if you circulated the cleaning solution around the coils? Kinda on the lines of a pump setup to clean a mod/con?