Dropping water pressure with extras - Help Please!

[MasterAbacus]

Hi everyone, dusting off the tools again and got myself involved in a bit of a renovation. (if there was an Emoji for hangs head in shame it would go here)...

While helping out with a bathroom replacement - and trying to work out the best shower solution, it seems the water pressure in the house, drops - considerably when more than one outlet is in use.

Scenario:
Gas Combi boiler only 3 years old and serviced each year, Water supply is old pre 1950s via what i think is a cast iron pipe, isolated in the garden (No Stop Tap I was told). The garden Isolation turn off the supply to 18 other houses.... found out when YW knocked on the door asking questions (Hangs head again)

Using the outside tap (nearest point to incoming supply) I get readings of 48 PSI static, then flush the down stairs toilet it drops to 24 PSI until cistern is full. If I run kitchen tap (Cold) it again drops to around the same.

Next door who I accidently isolated say they do not have any pressure issues.

So in my wisdom yesterday, I removed the back cupboard and it exposed as Ill post in the pictures... I found a Stop tap!... Well two actually! Top one works and isolates supply, bottom one no movement at all.

Any thoughts on things that could be causing the fluctuating oncoming, or ideas greatly apricated. . . or do I just run!!!

 

[Madrab]

The cold main looks like it's lead, certainly the connection into and out of the bottom stop tap is sweated (soldered lead connection).

What's needed is to get the water company involved and get them to check the mains pressure out on their main before it branches, a dynamic pressure and flow reading is needed.

Basically there is poor dynamic mains pressure and that could be down to a narrowed mains supply pipe (restricted/crush lead somewhere) or other restriction on the mains supply. That being said if it's 3 odd bar to start then drops to around 1.5 bar with just one other outlet isn't too bad, what does it do when more than one outlet is open, if it drops again then I'd be looking for a damaged pipe somehwere.

The mains may need excavated and/or replaced to improve the dynamic delivery.

 

[Londoner2]

I had a similar setup in my house, incoming was lead from boundary right up into kitchen, unknown to me for 14 years it splits into 2 pipes , one going upstairs and one going downstairs kitchen and toilet and boiler.

When ever we chnaged taps upstairs we had to turn a old stopcockl off, the rselut was pressure loss when tap back on and we had to play with both stopcks to gettig back, oftnn hit n miss and we struggled with it.

Then we had works done, new extension and had new 25mm mdpe to replace the lead pipe., problem sorted.