RO Reject Usage

[washtubman]

I want to use my RO reject water for HP rinse on my automatic. Will the following setup work:

Reject water is stored in 250 gallon tank with a submersible sump pump at the bottom. A 1-1/2" hose will go from the sump pump to the automatic rinse tank. A float switch in the auto tank will be wired into the sump cord and adjusted to turn on the sump pump before the city water float valve kicks in.

Comments appreciated.

 

[I.B. Washincars]

If you can mount the tank in the eq. room higher than the HP pump the sump pump is totally unnecessary. What I did was just mounted the tank next to my pump stand. I disconnected the original tank and plumbed the HP pump to the new tank. I set my float switches (the ones previously in the original tank) at about 6" and 12". I moved the fill plumbing from the original tank and had it dump right into the manhole. Any reject water also dumped right in there as well. With the top fill switch set at 12" this left room for about 225 gallons of reject water in this 4' tall tank. All it takes to do this is a tank and moving some plumbing. Most people that want to catch reject get hung up on transfering the reject water from the catch tank to the original tank. Don't use the original tank and this job is much easier, not to mention cheaper.

 

[washtubman]

I.B.,
Due to my equipment room configuration, I am unable to get it high enough, that is why I figured I'd go with the sump pump. Thanks for the input.

 

[Waxman]

I used a Little Giant submersible pump with 2 floats. One that calls for water and one that turns pump off if water level in recovery tank gets too low.

I had a plumber friend hook it up to be certain it'd work well and long-term. Mine is adjusted so that the ro reject comes on in tandem w/city water to feed the hp pump on my iba. That way I'm still using up all my reject yet mixing it with fresh water at the same time. I like it this way and it feels 'safe' to have the hp pump fed by both sources at once.

I looked at my p&l to see how much water I saved this way. Basically, I saved enough in water this way that the extra water used in my new detail shop (which is connected to city water and my old shop was not) is free!

 

[mjwalsh]

Maybe I am naive, but I wonder if a person could feed RO reject water directly into the city water line with 2 strategically placed check valves. The tank would have to be higher than inlet to the city water line similiar to what Pat said in relation to the HP tank.

It would add the 2 spring check valves but would eliminate anything electrical or floats. I am assuming that the makeup RO pump can lift the reject water high enough & overcome any resistance of a spring check valve to fill the overhead tank.

I don't have an automatic car wash just a 6 bay self serve so it is a little different than what you guys' setups are.

I have a prefabbed concrete roof & I am thinking I could size the tank just big enough for one reject fill & support it from the wall & roof. I can't use floor supports because the tank would have to be located in our 1st bay (12' high) adjacent to our low 7 foot high ceiling equipment room.

 

[MEP001]

You can't restrict the RO reject line to use that pressure. That's why the need for another pump to repressurize it. There's also the issue of how to use the water - while it's still soft, the TDS is much higher and it may act like hard water. You may not want to have it feeding rinse on a self-serve or mixing with soap or your customers will see bad spotting or reduced effectiveness of the soap.

Yes, it's actually a simple matter to run the RO reject to a city line with a check valve and a pressure-reducing valve, that way if the RO reject gets used up and switched off (A low-level float must be in place) the city water set at a lower pressure than the RO reject will just take over.

 

[cantbreak80]

How I do it?

With a relatively small equipment room for 8 ss bays, there?s not much room for large storage tanks.

The RO system is 4500 gpd (3 gpm)
The SFR water tank is 90 gallons
The rinse water tank is approximately 35 gallons

The RO reject is plumbed to the rinse water tank
The rinse water tank?s fresh water fill valve is adjusted to maintain approx 20 gallons
A float switch is installed near the top of the rinse water tank
A float switch is installed at the 75 gallon level on the SFR tank

When the SFR tank level drops to 75 gallons, the RO system is activated?unless the fresh water tank is full.

When the fresh water tank level drops to 25 gallons, the float switch completes the circuit to the RO machine?refilling the SFR tank and the rinse water tank.

One storage tank?no extra pumps?100% usage of the reject water

 

[mjwalsh]

Do--able?

You can't restrict the RO reject line to use that pressure. That's why the need for another pump to repressurize it. There's also the issue of how to use the water - while it's still soft, the TDS is much higher and it may act like hard water.

Mep,

You are getting us going somewhat. I wonder how tiny of a pump we could get away with to accomplish what you are saying about the absolute need for a pump? Also the pump & motor should be stainless because it seems that it would have to be mounted in the bay because of extreme space limitations behind the wall in the equipment room. The TDS level would be a non issue if I pumped the reject at the same time at least one large capacity washing machines is filling on a water line branch away from the car wash path. If the tank in the bay overfilled (a probable rare exception) it could run the small amount of overflow along the wall & onto the floor of the bay.

cantbreak80,

I could not use your exact setup because our individual rinse tanks from the OEM are tiny --- as in about 2 gallons capacity!

 

[MEP001]

This might make a little more sense for your setup. Use a small solenoid to allow a minute flow to the pump, controlled by the same voltage that starts the motor. You would need only a small repressurization pump, and possibly a valve to control flow to each bay so it's no more than the weep gun flows when released to prevent overflowing your individual tanks. The only question is if that's enough to use the RO reject as fast as it's produced. If you have a spare Flojet and solenoid you could conceivably test this with a bucket, some hose and a few fittings.

If it's not already a 1:1 system, it's fairly easy to reconfigure an RO system to only reject at a rate of 1:1. Most are at least 3:1.

 

[mjwalsh]

Hmmm-----Flojet does have pressures more than 60 PSI. So maybe this is do-able with air & water lines (no high voltage wiring) out to the 1st bay tank. 40-80 feet of 1/2 inch copper to the laundry water branch of piping also sounds do-able.

 

[washtubman]

When I started this thread, I had my reject plumbed to only one of my automatics (I have 2) rinse tank. I have since plumbed it to both. Then I adjusted the floats in the rinse tanks to let in the minumum amount of city water needed to operate, so that allows much more room for reject water in those tanks. Next, I adjusted my RO storage tank float to turn on the system at a higher level, thus not running as long to refill the storage tank. I am now using all my reject water and no extra pump or shutoff valves needed. Life is good!

 

[Dean Taylor]

Very innovative, great job! Keep us posted on how it works for you.

 

[Waxman]

Just be careful that while allowing the minimum city water in the hp rinse tanks, you don't create a situation where you could potentially starve the hp pump in the event of low ro reject available to the tanks.

After all, it really doesn't matter how much city water you add in with fresh as long as all your ro reject is being used, right?

 

[washtubman]

Waxman, I set the floats in the rinse tanks so they will operate with enough city water even with no reject water coming in. I just didn't need all that city water sitting in the tanks, so I lowered that level to allow more room for reject.