Fitting an S flange

[AndrewRanger]

Hi, I'm about to fit an S flange to stop air from causing my shower pump to surge. I've stopped the cold feed into the cylinder and run the hit taps to drain the water but the main pipe from the top of the cylinder is still really hot and doesn't cool down! I've got all hot water and boiler turned off. I'm worried that if I open the nut on the cylinder flange water is going to shoot out and I won't be able to get it back on!

 

[Hugh Jaleak]

If the hot taps have stopped dribbling then the supply to the cylinder should be off. You may get a dribble out the top of the cylinder as the contents find their own level, but if unsure, crack the joint where the supply comes out the cylinder, use an old towel to soak up any leakage and ensure it stops dribbling before undoing any further.

If you're relying on a Gate Valve to isolate the cylinder, you may find it wont completely shut off the flow and you need to drain the cold storage cistern too.

 

[AndrewRanger]

Is it best to run the hot water until it goes cold before shutting off the cold feed so at least any water in the tank is cold?

 

[Madrab]

There should be a drain valve on the cylinder, either at the cold feed from the cylinder or at the bottom of the cylinder itself, empty 1 or 2 bucket fulls out of the cylinder, in case the valve is passing, it'll give you some time to play with.
If the hot taps completely stop with the valve shut then hopefully the gate valve is holding ... Just make it a quick install if you can.

You could also bung the cold cistern and change the valve at the same time if needed.

One to remember .... have all the hot taps open when you're finished and you open the feed to the cylinder to try and avoid airlocks.

 

[Hugh Jaleak]

Is it best to run the hot water until it goes cold before shutting off the cold feed so at least any water in the tank is cold?

If you're going to do that, you'll probably need to drain the Cold Storage cistern to achieve your aim, so may as well shut the cold feed to the Cold Storage cistern feeding the cylinder off instead. Waste of hot water though if you dont need to do it.