Navien heavy knocking

[guido]

Starts at 40 seconds in:

Navien tankless 240
Heat circulation on

It's a new sound, we've had this tankless since 2016. Was inspected a year ago.

When I look at which pipe is making the most vibrations, it's a black pipe on the right side of the unit.

Should I turn the unit off immediately and have it inspected by a pro?

edit: the pipe that is knocking is connected to the expansion vat and the unit on the right hand side

 

[WorthFlorida]

Shut it down and check the expansion tank. Maybe full of water whereby the bladder failed or air leaked out on the other side of the bladder.

 

[Sponsor]

 

[guido]

How do I check the expansion vat? I read this: https://www.hunker.com/12276034/how-to-tell-if-an-expansion-tank-is-working

Knocking seems fine. I don't know how to check the pressure on it, there's not indicator or place to screw on a pressure checker

 

[guido]

Made a video of me knocking on it:

It also shows I've had a lot of leaking from the exhaust pipe. Not sure how to deal with it besides a towel on top of the unit

 

[guido]

Reddit plumbing tells me to look for a check valve, but I don't see one: https://photos.app.goo.gl/BpkPseBpm3nm5jsRA

 

[Houptee]

Remove the filter under the PVC intake air pipe (left side pipe on top). Watch this video.

 

[guido]

I think I found the real issue. Later I went upstairs and the toilet was making a stuttering sound too. I turned it off at the wall valve and since then it's been quiet. I replaced that toilets insides like 6 months ago, but apparently something is wrong with it now. Figured that out after I'm on hold with the plumbing company for 30 minutes of course.

 

[Houptee]

I would still check and clean the filter screen in the top of the unit they get all clogged up I had one causing problems and cleaning that screen filter resolved the issue with the Navien.
Also some Navien models have a trap for the condensation water that has to be cleaned periodically. Look under the unit for a plastic fitting with a metal wire clip you pull out. Then drop the plastic cap off and catch the dirty water in a bucket.
Both of those are basic maintenance on the unit so you should do it twice a year.