Powered by Blogger.
We are saddened to announce the passing of Gary Bunzer on April 17, 2020. We hope the RV Doctor website will continue to provide helpful information for you. Thank you for your interest and support for the RV Doctor - Debbie, Heather and Gretchen

Friday, October 30, 2009

Unwanted Hot Water

I had to replace all the fresh water piping in my 1982 Coachmen RV. I replaced the cold lines and then the hot lines so that there were no mistakes. But when I turn on the cold water in the bathroom I get hot water for a short time, then it gets cold. What's up?
Peter, (Nesquehoning, PA)

Peter, due to the layout of some floor plans, it's not uncommon for a cold branch of the fresh water system to be physically connected very close to the cold inlet on the water heater. And without a definitive method of keeping the heated water from backing into the system tubing, it's inevitable that some of the water in the cold line at the inlet will also be heated. During the time your coach was manufactured, it was rare to find a backflow preventer at the water heater, such as common today. If you are sure you have indeed replaced the tubing properly, try this; Install a one-way check valve (backflow preventer), directly to the back of the water heater at the cold, input line. Keep in mind the direction of flow. It should be positioned so that water will flow into the water heater but not out. My guess is that some of the heated water at that inlet area is being siphoned out of the water heater and delivered to that one faucet when it's opened.

To test this theory, fire up the water heater and open the kitchen hot faucet making sure hot water is indeed flowing. Then turn that hot faucet off and open the cold water at the questionable faucet. Chances are the problem disappeared. Why? Because as the hot water was running in the kitchen, cold water was automatically entering the heater eliminating that small portion of heated water near the cold inlet and that branch leading to the bathroom. Installing the backflow preventer should eliminate this condition by prohibiting any heated water inside the tank from migrating back into the cold line those few, crucial inches.


In all instances, every effort is made to ensure the correctness of all content on the RV Doctor Website. It is imperative that if you choose to follow any instructions or procedures outlined on any page of this website, you must first satisfy yourself thoroughly that neither personal nor product safety will be compromised or jeopardized.

All rights reserved.

If you are in doubt or do not feel comfortable about a procedure, do not continue. Simply call your local RV service facility and make an appointment with them. The advice, recommendations and procedures offered by the RV Doctor are solely those of Gary. They do not necessarily reflect the opinions, procedures and recommendations of our sponsors or advertisers.