off grid domestic water pressure system

[greenhouseparos]

will need to put together a system for pressurising the water for our house.
at the moment i have 35 cubic storage tank (the top of which is level with the floor of the house).
i have very little knowledge about plumbing systems and have some questions.
if i used a preasure pump with a 20litre tank how much water can you use before the pump starts (20l?)
if i use a preasure pump with such a capacity now and find out later it doesn"t satisfiy my needs can i add another tank.
what diffenrce is there between a 600w pump and a 1000w pump. does more w mean preasure is reached quicker?   
is any one off grid and using preasure pumps?

Paul     

[petertc]

Hi Paul,

Are you running 12 volt or 240 volt?

The larger the pressure vessel you have the the more water you can draw off before the pump come on, but the pump will run longer before switching off.

you need to look at the flow rate of water that you need and what pressure you need this will then determine what power is required for the pump, but you may have to take what power you have available, so i you have the washing machine running then you will be having the pump running.

You can add more pressure vessels into the system but it is having the pace for them buy the pump.

you usually have the pump then a isolation valve then a non return valve then the pressure vessel and a pressure switch then another isolation tap. this make the servicing easier as you can isolate things and also for error diagnostics.

if you are running a shower or bath then you will need to have enough supply for bot hot and cold feeds even if just feeding the hot water header tank.

I am using a 12 volt dc system for my rain water harvesting this has a flow rate of 12 litres min and up to 2.6 bar of pressure this is an on demand pump
but i added a small pressure vessel into the system.

[billi]

Paul 

If  you do not run   the pump for hours  and your  inverter is big enough  get this one  with no  pressure  tank ( but gravity feed the toilet )
http://www.alko.com.au/garden-products/al-ko-pumps/hwa1001-household-pump/

about 160 Euro in shops in Europe

[rogeriko]

You need a small pump because you are off grid. With a big pressure tank to keep the water going if the electric stops. My system is a 370w little blue pump from greek hardware store 70 euro. 80 litre pressure tank found by the roadside. pressure switch 8 euros. has been working for 4 years and when the electric stops we have about 60 litres of water still. You only have 3kw inverter do not let a greek plumber install any kind of grundfoss pressure pump they need 4kw to start. Go to your store and ask for the small blue cheap pumps they work fine 0.5hp no more otherwise all the lights go dim when they start.