Hot water, into loft pump - trickling out :(

[gsf600y]

My shower has recently stopped turning on.

It slowly got worse and worse...

• taking longer for the pump to kick in
• then would only kick in whilst fully on cold
• and now just doesn't start at all

I've disconnected the hot feed into the pump, and essentially there's just a slow trickle out of
the pipe, so it's no wonder the pump/shower isn't working properly.
Cold feed is good.

Hot taps (I've not drawn them onto the diagram) are working fine in all rooms.

The only thing I can think of, is that there is a isolating ball valve just before the shower pump. It's opening and closing just fine, but could it be possible it's blocked somehow, causing the trickle?

Pump is a Salamander CT50+.

Trouble is, I'm now confused - what would cause the hot feed to have slowed to a trickle?
Or, was it always a trickle, and the pump was previously able to suck the water up, but is now broken?

(Now, to my mind, the the hot feed into the pump should be coming directly up into the loft area, and feeding the pump that way, rather than going down to below the cylinder, and back up to the loft.
But this is what I've inherited when we bought the house. And it does work when it's working, even if it possibly isn't great for the pumps lifespan.)


Anyway, if anyone has any suggestions on how to diagnose what's causing this, that would be great.

Thanks.

EDIT: One thing I did try, was increasing the hot pressure by back filling the cold into the hot, via bath mixer tap. Dunno if that makes sense or not, but the water still trickled out of the hot feed into the pump.

 

[Madrab]

It's not about the flow at the pump, it's what flow you get at the shower head with the pump off, they will be different, that's what activates the flow switches. Not surprised you're only getting a trickle at the pump, if the pump's in the attic at the same height or just below the cold water cistern.

Firstly ... I'd be checking the pump filters/flow switches and any air vents you have. See what flow you have at the shower without the pump on. Filters in the shower may need cleaned too.

 

[gsf600y]

I've got zero flow at the shower with the pump powered off, and the temperature set to hot, OR cold.
Should the pump let water through even when switched off?

The pump filters are clean.....no air vents on it.
I've not looked at the shower itself. It's essentially this type:

 

[Madrab]

You need to work your way back from the shower.

Head of the shower on the floor - try .... remove the head - try ..... then the hose - try ...the mixer itself - try etc.