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Marc, Plumber
Category: Plumbing
Satisfied Customers: 1595
Experience:  Plumbing heating & home maintenance contractor
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Have a Rinnai unit, Just had the coil cleaned. Get hot water

Customer Question

have a Rinnai unit, Just had the coil cleaned. Get hot water for about 2 mins then it turns cold and doesn't catch up. Only happens on the showers
Submitted: 2 years ago.
Category: Plumbing
Expert:  Marc replied 2 years ago.
Hello and thanks for your question. I'll assist you today to the best of my ability.
Good morning and thank you for using the service, when completed, please remember to click on the smiley faces to rate the service I have provided.
With the explanation you have given, it is my professional opinion that the shower heads are possibly "low flow" water saver heads. The Rinnai heater needs to have a flow rate above 1/2gallon per minute in order to stay running and heating the hot water.
Since it does not happen at the other faucets, or tub (I assume), the logical explanation is to either replace the shower heads, or remove the water saver disk located inside of the shower head.
You may also consider turning the temperature of the hot water down on the rinnai unit (if it is up higher than 120) which will require less cold water mixed with the hot water within the shower, thus flowing more water through the rinnai heater.
I would recommend turning on the shower (at the setting normally used) and then going to the heater to see if it is running constantly during the shower or if it is shutting down. If it is shutting down, then the flow is too low.
Marc the Plumber