Water Still Running Through Shower After Valves Closed Down

[Grak]

Hi Folks,
Attempting to swap out shower pump after it failed.
I’ve isolated the cold supply (gate valve) that runs from loft through ceiling and down into the inlet of the pump.
I’ve also isolated the hot supply (gate valve) from top of hot water tank when goes into inlet of pump.
As a precaution before I wanted to disconnect the flexy pipes to the old pump, I thought I’d turn the shower on to make sure no water was running still.
Left it on for 5 mins and still hot and cold water mixed is still coming out of shower head (without pump force as it’s not switched on at main).
I’m pleased I tried this first without flooding everywhere!
Any thought anyone as the water supply has to go through pump before getting to shower mixer and the water feeds to both hot and cold going to the shower have been closed. TIA

 

[CountryFan]

Did it slow down at all? Are the gate valves definitely closed?

 

[Alec_t]

Gate valves commonly jam in the part-open state, due to lime-scale build-up.

 

[Hugh Jaleak]

Never rely on gate Valves to isolate the supply, invariably they jam up, shear off or as Alex has said, scale prevents the gate from closing right down.

You may find only option is to drain the System right down, and whilst empty, take the opportunity to swap any Gate valves for quarter turn Lever valves. Exercise these once a month and they should be good for whenever you do actually need them!

 

[Grak]

Strangely the gate valves are new and operate freely since we’d had a new bathroom installed and pump put in.
No build up at all on them of timescale.

 

[Hugh Jaleak]

Strangely the gate valves are new and operate freely since we’d had a new bathroom installed and pump put in.
No build up at all on them of timescale.

Then they're either knackered already or have some debris trapped in them, (unlikely to affect both though.)