Heating wash water

[Meaford Maples]

I would like to avoid using a heater on a wash tank if possible. When wash water is being recirculated, does it heat up to any degree as it is forced through the membranes or does it heat up because it is recirculated by a multi-stage pump (i.e. if I don’t use a multi-stage pump will it heat up regardless?)
Thanks
Steve

[jrgagne99]

It heats up some when recirculating, mostly from the pump I believe. I think certain types of pumps impart more work (i.e. heat) onto the fluid. I tried it once on mine that uses a deep well pump and it took over an hour to get 10 gallons from 50F to 90F. I wonder if one can you use steam-away water, tempered back to ~100F by mixing in cold permeate?

[Meaford Maples]

Using the water from the steamaway sounds like a good idea. I wish I had one...a project for another time.

[maple flats]

I use a tankless water heater, my Deer run RO does not heat the water very fast. The one I use is like this: https://www.ebay.com/itm/15429282425...Cclp%3A2047675
To use it I fill the wash tank with permeate at about 110F, then 3-4 minutes after I start the wash, I then use the tankless heater to heat the permeate portion and send it back to the wash tank. I use an infra red thermometer and run it until the wash tank is at 110-112F, then I finish the wash cycle. From what I understand higher pressure RO's heat the wash water without outside input.

[Meaford Maples]

The tankless heater isn’t a bad idea. Can you run that using a 20 lb BBQ tank?

[Super Sapper]

The tankless heater isn’t a bad idea. Can you run that using a 20 lb BBQ tank?

Yes you can, there are even 12 volt models if you do not have 110 at your sugarhouse.

[TapTapTap]

So it's never been clear to me whether proper RO cleaning is about a minimum contact time, gallons through the membrane, achieving the minimum temperature, or all the above. Obviously temperature is a very important. My shutoff temperature is set at 43 C and takes about 3 hours starting with cold permeate. I like the idea of starting with hot water (closer to 43) and still running a long wash cycle but the contact time and quantity through would be less since the time to reach 43 would be significantly less.

Ken

[Meaford Maples]

Back in the day when we could go to workshops, one presenter suggested doing a wash, letting it run up to temp, leaving it to soak all night and rinsing in the morning. That gives lots of contact time.
What volume of wash water is needed for 2 4x40 membranes?

[Meaford Maples]

I have power in the sugar house. I wired the RO closet with 2 15amp 120v circuits and a 20 amp 240v circuit. I use the 120v circuits for a feed pump and a room heater. If I unplug the room heater, I could run an immersion heater.

[maple flats]

The tankless heater isn’t a bad idea. Can you run that using a 20 lb BBQ tank?

They are made to run off a 20# tank, however, I have a bulk tank at my sugarhouse and a mainline with several take off's. My bottler used to be propane, my fire starter is a weed burner torch, my finisher is propane, my wall furnace for the RO room is propane and finally the tankless heater. All run off the smallest bulk tank, it's a 200 gal tank. Propane is far cheaper than if you go get 20# tanks filled. With all of those uses, I only go thru $140-160 a year.
Back when my only propane item was my first bottler, I used at least $80 a year just to heat syrup for bottling. While my bottler is now an electric WJ one, all that other stuff is propane.