Originally Posted by sforl
My Axis doesn’t have a single handle faucet.
Then if you don't have a single handle faucet, it is less likely that cold water would be mixing with the hot. If the cold water cartridge was leaking, then your shower would be dripping.
I assume the shower is the furthest away from the Tankless unit. If the hot water works in some places and not others your problem likely comes down to one or a combination of the following:
Incoming Water Temp
- In cooler / colder climates where the city water temp is relatively cold, the Tankless can have a harder time getting it hot enough before it leaves the heat exchanger. You can either try slowing down the flow (there is a white knob on the back of the tankless water heater that controls flow) or you can purchase a heated city water hose.
A few people have reported this type of problem over the past moth or two and it eventually turned out to be the cooler temps causing the incoming water to be realtively too cold and either slowing down the inlet flow or using a heated city water hose solved the problem.
Water Pressure / Flow
- The Tankless is very sensitive to water flow. When there is not enough flow, it won't fire up. This is easy to see happen when you turn on the cold water and the hot water simultaneously and the flow through the unit becomes too low.
It is important to have at least 45 - 50psi of pressure coming in from the city water. If the pressure is lower than that, it can be difficult to get consistent hot water. If the city water pressure is weak (or you aren't using a regulator to know and control the pressure into the coach), then try your onboard fresh water to see if the problem improves.
Flow can also be restricted from construction debris in the pex that starts to build up in different places over time such as the strainer on the pump or the screens / water restrictors at the faucets. I had flow issues on my last coach and when I removed all of the screens, they all had debris in them partially blocking the flow. Small pieces of plastic, wood, etc. get into the PEX and they don't blow out the lines before assembling them. Eventually they work their way through the plumbing and cam block the screens. You might want to disassemble the hose and shower head to see if there is a screen that needs cleaned.
There is another hidden screen to check. If you have the Girard Tankless, the Thor Factory Service Center told me that Girard puts a screen into the fitting where the water flow control valve is located. The Thor Tech told me they have been removing this screen when units come in for service ans people report water temp issuues related to flow. This screen has been getting clogged with debris and restricting flow into the Tankless causing issues. I have attached a picture of the schematics from the Girard Service Manual showing the screen. The Thor tech said with the onboard water filter, there should be no need for this screen. While that is true, you can still have construction debris in the lines after the onboard filter.
Now there could be an issue with the flow sensor in the Tankless unit itself, but I think you would see issues at other faucets as well.