I have a 1000ltr water at ground level. What would the pressure increase be at the supply pp if I raised it to 3 or 4 meters and increase the tank to 2000ltrs?

volume is irrelevant, it's the height of the tank and water level that affects pressure (1meter = 0.1 bar).

Not a lot! You need a pump. Cost around 6-7k baht depending on the pressure that you want. Mine puts out 42 PSI and cost me 6250 baht at Home Pro.

Agree with Wayned, simplest solution is a pump.

Something like this:

Moving to DIY

Pressure out the tank will be 3 or 4 times more than at ground level.

Hydrostatic pressure varies in direct proportion to depth. Volume is irrelevant.

To answer the OP (sorry)

0.1 Bar (1.45 psi) is equal to approx one metre of height between the bottom of the water tank and the outlet of the tap or shower.

1 metre height of water = 0.1 bar
2 metre height of water = 0.2 bar
3 metre height of water = 0.3 bar
4 metre height of water = 0.4 bar
etc

Also, don't forget that a full 2000L tank weighs 2 tons!

you just need a booster pump,

you dont have to go for the big expencive ones, your not drawing water out the ground, it will be gravety fed into your pump, so a smaller cheaper one will do the trick,

I already have a supply pp. But the wife has been told the reason it gets airlock is the electric gets low the pp slow down and pulls an airlock!

I think its a load of bs.

I was thinking on the line that if i had pressure from an elevated tank, i would have a supply even if no power and extra pressure for the pp giving a higher discharge at the tap.

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Is your pump above the level of the tank?

If so you may need an additional non-return valve to prevent the pump losing its prime (the valves in the cheap pressure pumps do wear and leak).

Do you run your tank dry? That would also cause air to enter the pump and kill its prime.

No to both. The pp is hitashi and 2 yrs old. I think the problem may be sand in the water.

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Your pump certainly won't like crunchy bits in the water, install a filter in the supply to the tank and clean out any sand that's already in the tank.

What model pump do you have (or post a photo of it with the cover off)?

What symptoms are you seeing when things go awry?

I wonder what it is that some folks think the water tank needs to be lofted for gravity feed supply. Well, it does if that's what you want. But, unless the main feed is higher and/or has pressure to supply the lofted tank, then you need a pump to get the water up there. More efficient that way but then you have a tower and more crap to deal with than a simple pump it out when you need it. Aaagh.

Unless you can place your tank on a hilltop 25M higher than your shower, it won't have pressure like a pump

Is it best to place the pump next to the house and the water tank away.

meaning my water tank will be 20 meters away from the house and I want to put the Pump right next to the house to get better water pressure inside.

Or do I need the pump next to the water tank??

Is it best to place the pump next to the house and the water tank away.

meaning my water tank will be 20 meters away from the house and I want to put the Pump right next to the house to get better water pressure inside.

Or do I need the pump next to the water tank??

Most water pump's need to be the same level as the bottom of the tank and fed with a 1" pipe, My friend had just the same problem some crazy Thai put it about 1MT below his tank and fed it with a 2" pipe after several attempts to put right we change everything and it worked ok still going 2 years later. Look at the fitting instructions. If you've lost them can get off the internet if you look up your pump name and size.

Remember water pumps make noise (in many cases a lot of noise) - so the further from sleeping areas the better. As long as not putting next to neighbors bedroom.