Flushing a Rinnai

[shak00]

Hi,
I'm flushing Rinnai tankless myself for the first time and have couple of questions. Hoping you guys can give me some pointers.

1) Rinnai documentation suggests flushing with a pump at 4GPM flow rate. Pumps I've found in some of the DIY videos and kits sold on Amazon are ~20/30 GPM ratings. What do you guys think, does it matter, can 20/30 GPM potentially cause a problem?

2) In my attempt to start the flushing process, I closed the hot and cold water supply valves, connected hoses, and then opened the service valves. I waited for the water to drain from the system before starting the pump. Cold water stopped draining in few seconds but the hot water side hose continued to let water out continuously. It was a slow stream, first hot, then warm, and then normal but it never stopped. I was collecting water in my 5 gallon bucket and after about 7 gallons decided to abandon the process and put everything back together. Any idea why such continuous flow?. BTW, I have Rinnai recirculating pump also part of this system (in case that matters).

Apologies for this long post.
Thank you.
Shak.

 

[TomFOhio]

Can you take a photo of how you had it hook up. That'll help alot.

 

[shak00]

Here is a picture of the tankless heater with valves showing and the steps I took after turning gas and power off to the unit.
1) hot and cold water supply valves were turned off.
2) Connected hoses on service ports
3) Opened the service valves.
This is the point where I wait for hot water hose to stop water flow but it continues as described earlier.

 

[Twowaxhack]

Turn both hot and cold valves off.

Go ahead and turn all the water off to the home.

Now connect your hoses and open the hot/cold service valves to the hoses.

With cleaning solution in the bucket and your pump running allow it to circulate for an hour or so.


I’m not going to try to figure out why you get flow from the hot side unless it’s necessary to find out….. Might be a tub valve crossing over a little. I don’t know how much water you’re getting back through the hot side…..and it shouldn’t be hot in temp unless you have another heater some place or the pipes are in the attic

 

[Twowaxhack]

Drain the heater before you start the process or you’ll dilute your cleaning solution.

 

[bobbycheetah]

Hope you got your tankless flushed ok. I found this post after I posted my question regarding pump flow of ~20/30 GPM. The unclear answer that I got directly from Rinnai, was "No, flushing at greated GPM will not harm the unit". I was just nervous b/c That Tankless Guy from Youtube says to flush at a greater GPM that the unit's max GPM rating. Anyway, I flushed mine with the Flow-Aide solution for 90 mins. I did go ahead and buy a Flow-Aide kit which includes a pump with a much lower GPM and will use that next time.