That would be fine for the house, but I think my current pump is just ok for that and I'm now looking to leave that in place anyway.A grundfos or salamander positive head pump should work. the newer ones are quiet and can boost low water pressure to >1.5 bar which is decent.
Current pump is 3.5bar but thats only at 9L/min which is very low flow.Have you got the spec on the current pump? too much pressure and you can break pipes. too much flow and you either wont get the benefit because head loss will restrict it or else you will drain your break tank too quick. What sort of piping size and distance have you got between your pump and your outlet where you wash cars? assuming you use a domestic hose rather than a pressure washer, a 3/4" hose (19mm) will help instead of the more typical 1/2" (15mm) as these are very restrictive. Alternatively, hook up a pressure washer.
You would be right about the pressure regarding the rest of the plumbing however I have decided to just keep the current pump and add a second which would be only for car and garden use so I could add new plumbing for that from the tanks as it would only be a short run. I've got two massive tanks at the moment and will add a third so I'll not have to worry about using up all the supply. The intent would be to use a 1/2" hose. I don't really like using a pressure washer for the cars most of the time, its just not needed and on my older classics it can force water where you don't want it.
Thanks. I'll get touch and see what they suggest. Will likely hit them up for a full plumbing upgrade like you have sometime in the future.I’d enquire with these guys www.dps-ni.com
They did a tank and pump system for me as I’m up on a hill and water pressure is poor, despite me running a new 32mm pipe the whole way up my fields from the water metre.
Depending what DPS offer I may just try the BuoQua pump, its a lot more flow and pressure than the current setup and isn't much money, might be worth a try. Has a two year warranty.
https://www.amazon.co.uk/BuoQua-Stainless-Centrifugal-Self-priming-Pressure/dp/B07F1SBP9J