How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask WCohn Your Own Question
WCohn
WCohn, Journeyman Plumber
Category: Plumbing
Satisfied Customers: 1038
Experience:  Journeyman Plumber/Estimator
6211579
Type Your Plumbing Question Here...
WCohn is online now
A new question is answered every 9 seconds

Water goes cold during shower then warms up again. For the

Customer Question

water goes cold during shower then warms up again.
JA: How long has this been going on? And how severe is the problem?
Customer: For the last year. I had a guy come out and flush the system which seemed to help for a month or so. Then it starts acting up again. It's only severe when your standing under the freezing cold water. :)
JA: Do you plan on doing the work yourself?
Customer: I have had this checked three different times to no avail. I am looking for an expert who deals with Renai tankless systems.
JA: Anything else we should know to help you best?
Customer: No. Do you know who I should contact to help me fix this problem?
Submitted: 10 months ago.
Category: Plumbing
Expert:  WCohn replied 10 months ago.

Hello my name is ***** ***** I look forward to helping you!

I am a Rinnai factory trained and certified installation and repair tech.

Customer: replied 10 months ago.
Do you know what the problem may be or who I should contact to come out to check it?
Expert:  WCohn replied 10 months ago.

Are you new to tankless water heaters? Are you getting any error codes?

Customer: replied 10 months ago.
Don't see any error codes and last guy says it's firing up correctly
Expert:  WCohn replied 10 months ago.

Do you know and understand what a cold water sandwich is?

Expert:  WCohn replied 10 months ago.

Are you still there?

Customer: replied 10 months ago.
Sorry. This was not the site I thought it was. Thanx any ways.
Expert:  WCohn replied 10 months ago.

We are here to give advice. I have your answer, but I needed to know what it is that you know and what your expectations are.

Customer: replied 10 months ago.
All set. Bye.
Expert:  WCohn replied 10 months ago.

Ok. You heater is doing its job. Just as it's supposed to. How it works has not been properly explained to you. This is common. Best of luck.

Customer: replied 10 months ago.
You are too kind. Thank you.
Expert:  WCohn replied 10 months ago.

I am more than willing to explain it all to you, however your previous comment leads me to believe you are not wanting that. Let me know

Customer: replied 10 months ago.
All set.
Expert:  WCohn replied 10 months ago.

Okay

All modern tankless water heaters have to prove it is safe to fire. Depending on brand this process takes about 8 seconds. During this 8 seconds cold water is running through the system. It checks fan speed, makes sure the exhaust can get out, waits for proof of flame, etc. This happens every time it has to start. So if you run hot water at a sink and wait for it to get hot, and then you shut it off and jump into the shower. You will feel the hot water already in the line and then the 8 seconds of cold water sandwiched between the hot water from you turning on the shower. If the heater itself was failing then it would give an error code. Usually a flame loss code or a blockage of venting. You are not getting any of that, so it leads me to believe its just a cold water sandwich

Expert:  WCohn replied 10 months ago.

Did I explain that well enough? Feel free to ask for clarification.

Expert:  WCohn replied 10 months ago.

I'd appreciate a 5 star rating. Your positive rating is the only way I get credit for helping you. Thank you for using JustAnswer!!

You can continue to ask questions after a positive rating.

You you'd like under another question I can explain how to get rid of the cold water sandwich

Expert:  WCohn replied 10 months ago.

Are you satisfied with my service? I need to know in order to close the question