What GPH/GPM pump is best for descaling tankless water heater?

[bobbycheetah]

Apologies in advance for being a bit long-winded...

Unit: Rinnai RU160iN
Manual: Max flow rate 8 GPM

I bought a Superior Pump Descaling kit from Amazon. It included a 1/6 HP pump. The chart in their manual shows at 5', is 29 GPM. I used that with the Flow-Aide (1 qt w/1 gal of water for ~90 minutes). The solution turned from orange-ish color, to clear with a bit of green tint. I asked a Rep at Rinnai who said there is not a max GPM to not exceed, and gave me a link to a kit they recommend to use. That kit has a pump that is rated at 20 GPM. My concern is that the Rinnai manual says: "Operate the pump and allow the vinegar to circulate through the water heater for at least 1 hour at a rate of 4 GPM" If I have a greater flow rate, can I simply run it for a longer time to allow the solution to work, or... is there a concern that the greater flow rate can cause harm to the unit? I watched many videos on YT and i thought one of the best was from "That Tankless Guy" here is the link - forward to 12:18 where he specifically mentions flow rate and not to go too high.

 

[Twowaxhack]

If the rinnai book says 4gpm, then stay around 4gpm.

 

[bobbycheetah]

If the rinnai book says 4gpm, then stay around 4gpm.

That's what I figured, so I went to harbor Freight and picked up a CreekStone 264 GPH @ 0 ft. which should be 4.4 GPM. I dont understand why Rinnai would provide a link to a kit with a 20 GPM pump. (I hope that my using 29 GPM for 90 mins didn't cause any harm).

 

[bobbycheetah]

update: I returned the pond pump to Harbor Freight. I went ahead and bought the Flow-Aide kit that is recommended by YouTuber - That Tankless Guy. Looks like the link I tried to include in my original post didn't make it.

fast fwd to 11:58
fast fwd to 10:53