Looking for a small plastic tank that will hold 7-8 PSI

Hello everyone

I have been collecting rainwater for about 15years and have been making changes in the set up I have as time has gone on.
I have a system that uses, what I call a first flush filter set up. It takes the first 60-70 gallons off the roof before I start collecting water.  If your not familiar with that, it keeps that first 60-70 gallons of water out of my collection tank.

So the water runs off the roof into a tank at ground level and then once full the waters starts backing up the fill pipe and then starts flowing into my collection tank. My collection tank is about 11-12 feet above the first flush tank. So once this takes place the tank from the first flush has a small amount of pressure on it, maybe 7-8 PSI.

I am looking for a Plastic tank that is approx. 24" round by 42 in high and will withstand this 7-8 psi. I have not been able to find anything that will hold any type of pressure.

Anyone know of anything?

I'm not positive it would handle the pressure but I think a blue plastic barrel with bung fittings (not a removable lid) could work.

Mike Haasl wrote:I'm not positive it would handle the pressure but I think a blue plastic barrel with bung fittings (not a removable lid) could work.

I'm with Mike on this -- a plastic barrel was my first thought also. Those plastic barrels are pretty tough, and they should be able to handle a few PSI which wouldn't be much different than thermal expansion for many products.

5-7 PSI seems like a lot for a water column. Offhand I suspect it's less.

Free options might included a discarded but sound pressure tank from a water well or cistern system. Not plastic, but designed for potable water. People sometimes upgrade to bigger ones. There are also fibreglass tanks for water softener systems that are pressure rated.

I've been looking at bio-gas for awhile and what I have found referenced in several locations is that a blue 50 gallon plastic barrel is rated at 100 kPa or about 14 PSI. Cross check me but a blue barrel should work.

It's not plastic, but a water heater tank is close to those dimensions, able to handle 40 psi, food safe,generally free and comes with threaded bungs.

The first flush units I use have a floating ball that rises the water flows into the flush tank and diverts clean water to the tank.
If your tank is not draining, the first flush will just go into the major tank.

Well I wanted to respond to everyone individually both for the life could not see how.

I did try a plastic barrel with a removable top and while the barrel is pretty heavy duty the lids are pretty flimsy. Once under pressure it leaked pretty bad from the lid.
I will look into the one with a fixed lid, and see that maybe the way to go.
I also like the ideas of going with a Steel tank out of a water heater or well tank. all good ideas.

There is a well drilling company right down the street I will stop in, they may have a old tank with a failed bladder, which I don't need.

Thank you to everyone!