Spotfree Holding Tank Size

[Officer]

Right now, I've got a huge silo tank in our chemical room, about 10-12 feet tall, for our SF water. Not sure the capacity. Another operator stopped by and said he uses a much smaller tank. What size tank is everyone using for their SF storage. I have a 3SS and 1 ACW.

Any benefits going smaller?

 

[MEP001]

No benefit in a smaller tank other than freeing up room.

The size of the tank you need is determined by the production rate of the RO unit and the maximum demand of the car wash. I used to operate a 6-bay SS and single auto with a 4.5 GPM (two membrane) production unit, and the tank never dropped below the point where the system came on. I could have used a 55 gallon barrel instead of the 350 gallon tank that was originally installed. It's good to have some reserve in case you have problems with the production unit, but even that 350 gallon tank would have run out in less than a day. Other than membranes slowly fouling and decreasing production, a system issue would have shut down the spot free rinse anyway.

 

[Greg Pack]

No real benefit at this point to go to the expense of buying a smaller tank unless you need the floor space. My tanks are big, and I rarely see them down more than a few inches. Ideally, The SFR production should be designed to keep up pretty well with demand. One strategy would be to replace the one huge tank with two smaller tanks and use one tank to hold and reuse reject water.

 

[MEP001]

One strategy would be to replace the one huge tank with two smaller tanks and use one tank to hold and reuse reject water.

I'm planning on doing that - I want to build a storage shelf on one end of the room and stack a couple water totes, one for RO and one for reject to plumb into the tank. It will free up nine square feet of room on the floor and help on the water bill at the same time.

 

[wash4me]

I'm planning on doing that - I want to build a storage shelf on one end of the room and stack a couple water totes, one for RO and one for reject to plumb into the tank. It will free up nine square feet of room on the floor and help on the water bill at the same time.

We did this and used a 0 pressure opening solenoid valve that opens with the same 24 volts that opens the fill solenoid valve on the tank. The 0 pressure valve is plumbed in between the top tank and the normal automatic pump stand tank.
I think it would be another good option with less moving parts to just use one large tank and eliminate the original automatic tank. Bottom one is low water shut off for pump protection. Middle one is city water fill level and top side is irrelevant because it is ro reject water that is going to overflow to drain if it ever gets that full.

 

[MEP001]

I use a large direct-acting float valve.

 

[Roz]

Our old tank was a monster at 800 gals. Went to the 10' ceiling and took up a lot of space. We changed to a smaller 250 gal tank that is fine for 5 SS bays and one Touch Free Razor. Never an issue even when we get slammed for 12 hours. The extra space we received from changing the tank was terrific for a work bench. This being said you should see at what speed you can produce Spot Free and guesstimate the usage if slammed. My guess is that you can get away with a 150-200 gal tank. Your IBA will use the most spot free as most customers do not bother in the SS bays since it is low pressure and they want to save money/time.

I have a new (extra) 165 gal tank with a float for sale on the forum as we miscalculated our max flow rate for the spot free and ended up we an extra tank (now in storage). Do the calculation and you can figure out your most challenging demand case for spot free.

 

[OurTown]

Roz if your 800 gallon tank was a monster then what would you call our 1,500 gallon tank? Most of our SS customers use our spot free. It is 400 psi. Now if I could get most to use pre soak.....

 

[MEP001]

Roz if your 800 gallon tank was a monster then what would you call our 1,500 gallon tank? Most of our SS customers use our spot free. It is 400 psi. Now if I could get most to use pre soak.....

How do you have the presoak set up? I run the pressure at the highest a FloJet is rated for, 3/8" ID tubing, no flow adjustment on the liquid, and set it up with the least amount of air I can get to the bay to make it barely foam. IMO if a customer has to spend more than a couple minutes to cover their car with presoak, they won't use it.

I've seen a spot free storage tank that must have been 4000 gallons. I still don't know why they had such a huge tank since it never dropped more than a 1/4" below the full line.

 

[OurTown]

How do you have the presoak set up? I run the pressure at the highest a FloJet is rated for, 3/8" ID tubing, no flow adjustment on the liquid, and set it up with the least amount of air I can get to the bay to make it barely foam. IMO if a customer has to spend more than a couple minutes to cover their car with presoak, they won't use it.

Right now it is on a well pump and runs about 35 psi and has no air injection. Hey...I didn't build the place. I can cover my large truck in three minutes with that setup which sounds similar to what you are talking about. We will most likely put it on a Flojet and inject air when we do the big remodel.

I've seen a spot free storage tank that must have been 4000 gallons. I still don't know why they had such a huge tank since it never dropped more than a 1/4" below the full line.

Was that tank above ground? Ours is underground and we were thinking of putting a small tank (150 gal?) above it with a transfer pump from the underground tank to it so the HP pumps don't work so hard lifting.

 

[MEP001]

Was that tank above ground? Ours is underground and we were thinking of putting a small tank (150 gal?) above it with a transfer pump from the underground tank to it so the HP pumps don't work so hard lifting.

It was in one of the three equipment rooms. It must have been brought in before the bricks/blocks were laid for the walls.

I've seen another wash with a huge underground tank for the RO. They used a 100 gallon tank on the second floor to feed everything and had a Flojet to pump it up to the tank. They just used a float valve in the upper tank and left the pump with air pressure all the time.