Rinnai RUCS75i no flow

kevinlee00 · Apr 8, 2023

No flow this morning from hot water faucets, checked multiple faucets. It would build pressure after a few minutes so you would get a splash of water and then instantly down to just a drip every 1/2 second or so. It resolved itself in about 1/2hr. Indoor installation and 40 degree temps, so not a freeze issue. We have hard water mineral issues, but never 100% block of flow. I guess my question is if the internal valve in the Rinnai can completely close??? I know they regulate flow to achieve desired flow, but can they completely close due to malfunction? Although it was nice to have hot water again, it would have been much better if problem would have continued so I could isolate it. I plan to check Rinnai filter later this morning, but because of the design of filter, i doubt a chunk of calcium could block it entirely and then magically not block it. I'm going out of town in couple weeks and will have someone here dog sitting, do not want some poor dogsitter to suddenly have no hot water!

Twowaxhack · Apr 8, 2023

Check the inlet filter. Check for trouble codes.

kevinlee00 · Apr 8, 2023

no trouble codes. I will check filter. Just didn't seem likely a round filter like that would be able to be completely clogged and then completely unclogged, but I will check it.

Twowaxhack · Apr 8, 2023

Next time it happens go to the unit and if it has service valves, check for water at the hot and cold.

kevinlee00 · Apr 8, 2023

Twowaxhack said:
Next time it happens go to the unit and if it has service valves, check for water at the hot and cold.

Yeah that was my plan. I had just moved a couple things that were in front of the unit in order to get some hoses on. Decided to check faucet one more time and then had water. Very frustrating! Intermittent problems are not as fun to diagnose!

Twowaxhack · Apr 8, 2023

kevinlee00 said:
Yeah that was my plan. I had just moved a couple things that were in front of the unit in order to get some hoses on. Decided to check faucet one more time and then had water. Very frustrating! Intermittent problems are not as fun to diagnose!

Could you get any cold water at the time the hot wouldn’t flow ?

How old is the unit ? Have you ever cleaned it ?

kevinlee00 · Apr 8, 2023

yes, cold was fine. Unit was a 2016 install and its been flushed many times, probably averages at least twice a year flush. My water is very hard and mineral deposits are constant problem. I guess it all points to that filter.