After camping in the "wild" and having no problems, we hooked up at a campground and have VERY low flow of just the hot water.

Contact their Support direct. It may be low water pressure.

https://www.eemax.com/products/eemax-flowco/spex3512

..

turn the heat down or turn to pilot mode. Turn water supply off, hook up hose to drain valve, route hose to safe place to drain, v if this is above grade the don't turn the water supply line off. Open the drain and see how well it flows. There could be calcium deposits in the unit. IF it flows well out of the drain, you could have corrosion build up inside the inlet or outlet from minerals. Remove the inlet and outlet connections. Check for debris, you may have to replace the washer on the unions. Check the anode on the unit.

Oh some of these there was a small black heatexchanger just for hot water they some times block up . or it could be a blockage in the water section where it flows in .I know Valliant have a very good tech line and fitters who do house calls .

You have clogged pipes, pipe moves against wood surface because it is not strapped, or pipe is missing air chamber. Or all three.
http://waterheatertimer.org/images/Flow-rates-water-hammer-600.jpg
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#bang
http://waterheatertimer.org/Low-hot-water-pressure.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Hi Bob,

You can determine if the tank is the problem by connecting a garden hose to the drain that is provided on most water heaters. Before doing this, be sure to shut of the electrical supply to the heater - otherwise you can damage heating elements if an electric type or waste fuel by heating an empty tank if a gas / propane fired type.

If you get a slow flow out of this drain, it means that somewhere in the cold water supply side to / in the tank - there is a problem. Inside the tank, the cold water is delivered by a "dip tube" that distributes the cold water to the bottom in the tank. Dip tubes are used in both electric and gas / propane fueled heaters. Here's a cut away view of a typical tank:





If the tube is clogged, or there is build up, scale or debris in the supply (cold water) side of the heater, flow rates will suffer. Likewise, if there is a problem with the output of the tank, it will directly affect flow as well.

If you get a good flow rate from the drain, then the issue is going to be on the hot water output side of the heater. Again, the same build up, scale, debris issues on the hot water out put pipe will cause problems with flow. Typcial tanks do not have dip tubes for the hot water side of the tank - as taking hot water from the top of the tank is most desireable and is furthest away from the cold water that rushes in to make up the hot hot water going out.

There's nothing really in the tank itself that can cause issues with flow outside of the dip tube, and piping to and from the tank.

Good luck!

There is a minimum water flow required to operate your Bosch tank-less water heater. It is around .75 gallons a minute. There are three things you can do to help the flow.
1.Turning the temperature down will help increase the flow.
2. Installing higher flow aerators on your faucets.
3. Clean the Bosch tank less water heater.
You are not alone in having this issue. The most common problems are low flow faucet aerators and low flow shower heads.

Sounds like you have a problem with water flow. Since your ground water is warmer in the summer, you mix less hot and more cold in order to get the same warm temperature. If your hot water flow gets low enough, your tankless will start to "short cycle" in order to prevent scalding. Use one of these three methods to increase your water flow at the shower:

1) Clean your shower head and descale
2) Widen the hole in the showerhead's flow restrictor
3) Remove your flow restrictor entirely

Good luck!

Sounds like you have a problem with water flow. Since your ground water is warmer in the summer, you mix less hot and more cold in order to get the same warm temperature. If your hot water flow gets low enough, your tankless will start to "short cycle" in order to prevent scalding. Use one of these three methods to increase your water flow at the shower:

1) Clean your shower head and descale
2) Widen the hole in the showerhead's flow restrictor
3) Remove your flow restrictor entirely

Good luck!

I have a triton opal shower.

I turn shower on low pressure and cold water. then no low pressure and piping hot water for a very short time then low pressure and cold water.

I've changed the solenoid and the little black plastic ball.

Help !

most likely the diverter valve.. when hot tap turned on the movement of the water through the valve operates a diaphragm which pushes a pin/button//switch to tell the boiler to fire up