Cold whether and shower pumps

[srmans]

I have noticed recently that the pumps to my showers have to work harder in this cold weather. I expect the cold supply from tank in loft is ~2 degrees and the hot water is at ~62 degrees. It seems the hot pressure drops over the course of a 4 minute shower.

The pressure on the hot supply of the pump is the same as the cold at about 0.3bar which I understand is approx 3m head which matches the pump/tank locations. I was wondering if increasing the down pipe to the hot water cylinder from 22mm to 28mm would help alleviate the pressure drop felt at the end of the shower?

Perhaps it is just aeration, any ideas?

 

[Simon F]

an increase in pipe size could give improved flow, but will not affect pressure,
that is determined by the head of water and the pump wattage.

how is the hot draw off connected to the cylinder?

is the cold tank sufficient size ( 50 gallon/200 lt )

 

[srmans]

The hot is drawn off through a Surrey flange and the cold tank is 50 gallons in size. I've installed all the pipe work myself so I'm satisfied there are no installation mistakes.

Perhaps it is just my imagination but I see it by running the mixer on full hot at the start and it shows the initial flow and then at the end of the 4 minutes, again on full hot the flow is reduced.