Poor gravity circulation for HW

[Radio Fixer]

My first post to the Forum so Hello to all and thanks for any answers

We have a 30 year old system apart from a replacement boiler and pump about 3 years ago and some new rads.

The CH is pumped as normal but the HW circulates on gravity. It has always been fine but now seems very sluggish and difficult to get a decent tank of HW.

When the new boiler was fitted a piece of 15mm pipe, with an S bend, was cut out of the cold fill from the header tank as the system wouldn't fill. I am wondering if the cylinder coil has a similar blockage. Is this likely or do the coils use a much larger gauge of pipe that is less likely to clog?

Yesterday I put in some Sentinel X400 but wonder if that will be effective with garvity circulation?

When I drain the system to remove the X400 and hopefully lots of gunge I could remove the HW cylinder and flush this separately, am I going to a lot of trouble for nothing?

thanks Gary

 

[P4ULT]

need to check th tank is full of water and the ball valve working. is it primatic

 

[danielp]

turn the heating on check the two pipes touch the flow to see how hot it is and then touch the return to see if a bit cooler but both should be really quite hot

 

[stevetheplumber]

need to check th tank is full of water and the ball valve working. is it primatic

if its primatic they would be washing in fernox

 

[Radio Fixer]

No! not primatic

Pipes were and still are inbalanced for heat. The X400 has already made a slight improvement. Plenty of water in the header tank and ball valve OK

When I take out the X400 is it worth taking out the cylinder for a good flushing? Are they known to clog or is a blockage elsewhere more likely? Would replacing the cylinder be better?

thanks