How do you adjust the pressure on a watts regulator to increase the flow of water?

the low pressure/flow minimum is for safety and protection of unit and no adjustment to do so

Backflow preventer is not part of water heater:
http://waterheatertimer.org/images/Watts-water-heater-parts.jpg

Water heater might have heat trap nipples that get clogged... but other issues have to be eliminated:
http://waterheatertimer.org/Low-hot-water-pressure.html

Gene h

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

Even a small amount of crud on the rubber washer/sealer can cause the valve to seep. Some valves can be taken apart and cleaned but it will be better to replace the valve. They can be found on line for around $12 or more. You will have to shut off the water in take valve and drain most of the system unless you have a main line shut off valve so the system wont drain back into the boiler. These valves are usually set at 30PSI.

1. COLD MIX, HEATER DEACTIVATES
   If inlet water temperature is over 70°F due to geographic location, water maybe very hot out of the tap. This requires a lot of cold water to be added with it in order to attain a useable hot water temperature. The addition of too much cold water will overpower hot water demand from the tankless water heater. This slows the flow within the tankless water heater, decreasing it below activation point, which shuts off the heater. The end result is nothing but cold water coming out of the outlet. See: TWH E2-04 Overcoming fluctuating temperatures [PDF].
2. FLUCTUATING WATER PRESSURE
   If the water pressure in the home is erratic and the water flow is not consistent while a tap is opened, then the temperature of hot water will fluctuate. The minimum water pressure for the home should be 30psi or greater. For people on well systems the minimum pressure range is 30-50psi. The use of a pressure reducing/regulating valve is an effective way to maintain constant water pressure to the water heater. Watts brand 25AUB- ¾" or N35B-¾" pressure reducing/regulating valves or equivalent is suggested.
3. CHANGING FLOW RATE
   Major changes in flow rate can adversely affect the output water temperature of the heater. Increases from one major fixture running to multiple fixtures running at one time can cause the temperature to fluctuate. Stay within the heater's specifications. See: TWH E2-03 Outlet temperature vs. flow rate [PDF].

From the Bosch website.

Good Luck,
Gary

Hello The 740 is NOT EVER!!! adjusted.It is factory set.It can be purchaced at any PRE-set rating from 30-75 LBS.You MUST match the rating of the old one.If in doubt use the 30# to be safe.

Biggest problem with this is the LP piping and gas pressure. It needs a higher gas pressure than the regulator is factory set for. Have your gas company or licensed plumber increase the pressure and check the flow (with all gas appliances on). Bring it up to 11 inches of water column with everything on. This will usually fix the problem.

The gas pressure must be increased at the regulator from 9 inches of water column to about 12.5-13 inches of water column. The CO2 levels need to be adjusted for each installation. The air intake MUST come from outside the same wall as the exhaust. I have never seen any manufactures tankless unit installed properly. Plumbers do not read the manual.

On the top of the regulator is a stem/threaded rod with two nuts on it.

Loosen the bottom nut and that will allow you to turn the stem, which adjusts the pressure.

clockwise usually increases pressue, although I have encountered PRV's (Pressure Reducing Valve) that decreases pressure with a clockwise turn.

When A PRV starts malfuntioning, they often cannot be adjusted and need to be replaced or rebuilt.