I’m in the process of installing a pumped mixer shower. Previous set up in the house was mains cold piped direct to each outlet. Only the hot water system was supplied by the loft header tank.

I’m conscious that a pumped system could empty the header tank very quickly as both the hot and cold pumped feeds will draw from the same tank…

So, I’m planning to install a new 42 gal. tank in the loft space.
My questions are:

1. Replace existing tank? Seems like unnecessary additional work???

2. Retain existing tank as header for hot water system and add new tank as separate cold water feed for shower pump?

3. Add new tank, but with a connection to the old so that they operate as a single volume?

No. 3 :making sure that the take off point to the pump is on th opposite side to the float valve and the supply for the hot feed to the pump is 25mm above the cold feed so I the cistern runs dry for any reason, you’re not scalded.

https://www.google.co.uk/url?q=https://www.wras.co.uk/downloads/public_area/publications/general/information_note_guidance_for_connecting_storage_cisterns.pdf/&sa=U&ved=0ahUKEwiS18G70fjPAhXhI8AKHY2lD6UQFggOMAE&sig2=xkvkDXAS0uWiiIYIPvdEDA&usg=AFQjCNHAW4es2nXXyODBaw5G-SN4SCum0g

Ta.

I was favouring No 2 or 3 – less faffing. Take off for pump cold would be from the new tank either way.

No. 3 avoids separate supply and overflow etc

Install a matched pressure system and remove header tank altogether?

What cbike said, just done this and improved the performance of our system a lot

We’re hoping to match the pressures on the shower supply by installing the pump…

If you’re meaning a matched pressure system for the whole house, using an unvented tank or heatstore, then that’s pretty much out of the question (£££)

I did this about 10 years ago and replaced the old galv tank with a new plastic one. Fairly easy with push fit stuff. Only issue I came across was the loft hatch wasn’t big enough!! Duh. Spent a day I didn’t have space making a bigger hole in the ceiling! We used a 3 bar pump which was a bit noisy but great pressure. Again all easy with push fit.