[dudek]

Hi guys,

Im trying to set up a water harvesting system and was wondering how high i would need it to be for the gravity to do the pumping into the van.

Ideally I will be buying a 7000 litre tank that will take a lot of water from 2 warehouse roofs and a small lean to all converging at one point into the tank.

I'm worried it will have to be so high that it wil be above the drainage points thus defeating the whole project.

Can anyone help?

Dudek

[daz1977]

buy a pump it will be quicker and easier than waiting for gravity to work, unless u will fill from a large hose in to your van then you have to have the storage tank off the ground by about 10 mtr to make it work as 10 mtr = 1 bar of pressure,  and then this might not fill up quick enough

its really big 7000 ltr, do u have the sizes for it

the mains tap pressure on a house is usually 4 bar   to get that off a tank you need to raise it 40 mtr

put tank on ground and use a pump to fill up ur van,

[dudek]

I need to do it the gravity way and the outlrt will be 2 inches so once we have some decent water in the should gush out but wanted to confirm wih any rain water harvesters out there?

Dudek

[NWH]

£70-£100 sub pump in the tank will do it better than gravity.

[daz1977]

if you dont want to use a pump, then the btm of your storage tank has to be higher than the top of your van,  also to create enough pressure the tank has to be tall rather than wide, as this will create more pressure,  other wise it wont fill up properly

i know as the principal is the same as a shower working of a tank in the loft, just on a bigger scale

best thing you can do is buy a pump

[ftp]

Just got to be higher than the tank inlet to get it to syphon. Say four foot? What happens if it doesn't rain for a month?

[michael papworth]

Yes, you're right. The flow rate will depend on the head of water - the vertical height of the top surface of the water above the outlet.

It also depends on the diameter of the pipe. A 2 inch pipe should flow fast enough even with a small head of water.

[sparklebright]

Mate of mine had his tanks on top of a shipping container. The water fair gushed into the van. He had his system make the water then he and a couple of others would come and fill up by opening a valve on the pipe, worked fine.
But remember a 7000 litre tank will weigh 7 tonnes.
So you will have a job supporting it above ground level.
Sump pumps are pretty good actually

[AuRavelling79]

The key to fast gravity filling is a big bore hose (say 2.5"/3").

I have a 600L IBC tank which stands on breeze blocks slightly angled towards the outlet and the outlet is about half a metre off the ground. The top of my van tank (400L flat type) is about 3" lower than the outlet.

I have a transfer hose which is about 3 metres long and 2.5" wide which fits over the tap of the IBC.

It takes but a few minutes to fill my van tank from empty. All done by gravity alone.

[Ian Lancaster]

I have a 600L IBC tank which stands on breeze blocks and so the outlet is about half a metre off the ground. The top of my van tank (400L flat type) is about 3" lower than the outlet.

I have a transfer hose which is about 3 metres long and 3" wide which fits over the tap of the IBC.

It takes but a few minutes to fill my van tank from empty.

Exactly

You don't need a huge head of water to get it to flow - a couple of centimeters will generate a good flow rate if the connecting pipe is of a big enough diameter.  2" will give a good fast fill time.

All you need to be sure of is that when your van tank is nearing full, the outlet from your storage tank is still higher than the inlet to you van tank.

[dudek]

Thanks for the contributions guys, the reason i cant use a pump is that i have a problem accessing electricity.

So the outlet needs to be slightly higher than the very top of the tank in the van?

Dudek

[michael papworth]

Pretty much. To be perfectly accurate, the lowest level of the water in your 7000 litre tank needs to be higher than the highest water level in the van tank.

[dudek]

Thanks wally appreciate your time clarifying that mate.