Friday, June 9, 2023


My on-demand water heater is not hot. Did I do something wrong?

Hi Dave,
I just brought my RV out of storage, hooked up to city water and ran out the antifreeze. I find the hot water is only warm now, not very hot. It was fine when I winterized and put it in storage. I have an on-demand hot water system. What could have gone wrong with it or have I done something wrong?

It’s a Girard Model GSWH-1M. I have noticed that the more I use it, the better it gets as far as temperature, plus the lower the flow from the tap the hotter it gets. I am wondering if there is a maintenance program that I am not aware of to keep it operating tip-top, or is there something failing? Thank you for your time. —Gerry, 2014 Jayco Greyhawk RV

Hi Gerry,
I am not that familiar with the Girard on-demand water heater system; however, a little research led me to Lippert, which purchased Girard in 2022. My Lippert tech contact had a few ideas and then sent a link to the installation and service manual.

Purge air in water lines

You need to first purge any air in both the cold and hot water lines, which might be why it is getting better with usage. Next, there is a Gas Modulator Dial (GMD) that can be set according to the ambient temperature. Moderate temperature is set to the middle, extreme cold is set to the far right for a larger flame, and hot temperatures set to the far left for a smaller flame. Make sure the water heater power switch is in the “on” position.

Turn the hot water faucet on and set it to normal flow, which is 1/2 to 2/3 pressure. Let the water flow until heated water from the Girard system gets to the faucet. This could take a while depending on the distance of the faucet. If the water temperature is not hot enough, turn the dial clockwise to increase the flame/btu. Do this slowly as a fast temperature rise could set off the limit switch.


The only maintenance listed in the manual is to open the relief valve once a year and then visually inspect the rest of the unit for dust, debris, cracks, and other items. However, there’s nothing that would really affect operation. One thing the tech suggested was to visually inspect the flame through the sight hole to make sure it was a continuous blue flame and not jumping, flickering, or have an orange portion to it. If so, there is an issue with the proper combustion, and you would need to have the LP pressure tested coming to the unit. He also suggested cleaning out the burner assembly with an air hose, like how we clean the burner assembly of an absorption refrigerator. This would blow out dust and soot to make the flame more consistent.

Verify the flame is going

When you experience the lack of hot water, verify the flame is still going. If the gas module dial is set too high for ambient temperature, the water will get over 131 degrees and the limit switch will shut it off periodically. Another issue if the flame is not burning could be the sail switch, which is a triangle metal in the exhaust pipe. The blower is designed to blow air out the exhaust, which pushes the switch. It then creates a closed circuit, sending 12-volt power to the module board telling it to light. Check to make sure this switch is not getting stuck and might need a little cleaning with CRC electrical cleaner. Note: All this is done with the unit off and cold.

According to the manual, the system can be set between 18,000 btu to 36,000 btu, which will heat incoming water 20 degrees to 70 degrees. If you are connected to an outside campground source, that water could be a little too cold for a normal setting.

If all this does not fix the issue, contact Lippert at and they can walk you through testing the ECO, thermostat, and other components if you feel comfortable going that deep.

 You might also enjoy this from Dave 

Can I install a single on-demand water heater for RV’s kitchen and bathroom?

Dear Dave, 
I purchased this trailer in November 2021 from Lazydays outside of Memphis. It was known I was taking the trailer to my home in Maine. The trailer was parked all winter in Maine. In the spring I took it to my lot in Northern Maine. Well, all the water lines were damaged, and the water heater didn’t work. Lazydays apparently hadn’t winterized the trailer, and I never asked them if they did. My question is, can I install a single on-demand water heater that would take care of the kitchen and bathroom? Usually, it is just me at the trailer, so I don’t use a lot of hot water. Your sage advice will be appreciated. if my solution isn’t feasible, any advice? —Bill, 2018 38-ft. Keystone Cougar fifth wheel MKS37

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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Tom H.
28 days ago

What about the outside shower valves (if so equipped)? I know that if the hot and cold valves are open but the hose isn’t connected/open that cold water will mix with the hot effectively lowering the temperature.

28 days ago

I have an older whole house tankless heater. It also has an adjustable flame modulator. The water temperature depends on the temperature of the incoming water. Mine raises the temp 80º of the temp of the incoming water, so flame adjusted accordingly. It requires at least a 1/2 gallon/minute of water flow to allow the flame to ignite, not the pressure of the water. Probably similar to the one mentioned. This is one that does not have all the electronic sensors to operate.

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