Combination valve fault issue low pressure

[brierleystuartj]

Have a combination valve with 6.5bar incoming pressure. The valve would have been set at 3 bar presumably, but the property is having lower than normal water pressure from the outlets and operating a second outlet dramatically affects the first outlet. Once the issue was noticed the static pressure was down at 2.5 bar. After adjusting back to 3 bar the original issue, that the pressure over the whole property is lower than normal, not being maintained at 3 bar or the 2.5 bar it was set at for some unknown reason, and being affected by turning on a second outlet, is still present. Cleaned the filter which did have some crap on it and flushed the valve. The spring mechanism moves relatively freely but cant say i have a reference to know what a new mechanism would feel like. The issue still remained. The hot and cold are both affected as the cold outlets are off the balanced outlet off the valve. Anyone have any experience of a similar issue? Does a valve adjust from what should have been 3 bar, down to 2.5 bar because the mechanism is faulty? It all looks clean and healthy and cant visually see anything faulty with bellows or spring.

 

[ShaunCorbs]

Do you have any outlets before the combi valve ?

 

[brierleystuartj]

There is a feed before the combi valve to an outside tap. There is also a thermostatic mixing valve feeding a second outside tap that also takes its cold feed from the same pre combi valve feed. Its a Bristan TMV3 that has check valves built in but having just looked up the install instructions has a max operating pressure of 5bar. Could these check valves be pushed open so 6 bar cold is back feeding down a 3 bar hot feed through the TMV. Surely not, and that would increase the pressure not lower it unless its creating some imbalance and Soding the system off.

 

[ShaunCorbs]

Can you take a flow and pressure reading out of the Outside tap pre combi valve

 

[brierleystuartj]

The 6 bar incoming reading is from the cold outside tap as the combi valve doesn't have a gauge and that's the only outlet not running off the balanced outlet. I did take flow readings but i have lost where i wrote them down. From memory that outlet was 22lpm. The kitchen outlet was down to 18/16lpm with just the one outlet running

 

[brierleystuartj]

Apparently it worked fine before the TMV hot tap was fitted so maybe it is to do with that. Can you get check valves that are rated to higher pressure or should i just take a cold feed for the TMV from the balanced cold and just leave the cold outside tap on full incoming pressure.