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Can you reverse flush an On Demand Hot Water Heater ?

2851 Views 3 Replies 2 Participants Last post by  gladesteen
Hi all,

Had a situation in my Water Well where ants moved in. That problem is solved, but the clippings and debris they dumped into the well are still an issue. I've got it almost gone by running my outdoor faucet with cheesecloth as filter.

My Rinnai Hot Water heater inline filter was completely clogged up. I removed that, cleaned it and ran 2 gallons of vinegar through the system, but its still not flowing like it used to. I've checked the online filter, even left it out and still the same thing on the hot water side. Lower than usual pressure.

Can i REVERSE the flow ? Meaning hooking up the sump side on HOT and exit side on COLD to reverse flush the Rinnai ? Any damage or check valves ?

Thanks, Mark
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Larry, yep exactly like that !

I had to use 2 gallons of Red Wine Vinegar, because i couldnt find regular stuff anywhere. But yesterday, on one of my many Home Depot trips, I noticed 30% vinegar gallon bottles up front. Sucks they're $20 each, but I'm going to get 2 of those and try to reverse flush this sucker tomorrow.

I will probably dilute the 30% vinegar as its pretty strong just to be on the safe side.

Forgot to mention that i also cleaned the shower heads and sink aerators as well.
Returning back to say.... IT WORKED !

I now have the most pressure since the Rinnai was installed. Very small pieces caught in my outlet hose ( i cover the end with cheesecloth ) during the Rinnai cleaning.

What i did do different this time was allow the vinegar from inside the Rinnai to circulate up to the Shower head, Kitchen faucet, and Bath sink, then i shut everything down and let everything Sit and Soak for 30 minutes.

Purged the Rinnai from the Vinegar, cleaned my sump with fresh water, fired everything back up.....MASSIVE pressure difference in Shower. I mean night and day. There was quite a bit of 'Gunk' that came out from having the vinegar sitting in the lines......i think thats what made such a huge difference.

Thanks! I am psyched !! Heading to the shower......
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