Cleaning used membrane

[Bricklayer]

A friend of mine gave me a 4 year old used xle-4040 membrane. It was used with well water to make permeate for washing windows. He only ever did warm water rinses with 65 gallons of permeate every 2 weeks or so. I've been using it to test my RO for leaks and to make sure pressure switches work etc. It seems to flow pretty good and I can get a 8 gpm concentrate to 1.3 gpm permeate flow with my well water.
I don't plan on using this membrane for sap but I would like to do a soap wash and acid wash on it to revive it. I figured it's nice to have an extra membrane that I can make some permeate with in the offseason for various things. and have the tanks full of permeate for rinsing come sugar season.

What should I do to clean this membrane. Acid then soap or soap then acid?
I just picked up a 5 lb bag of food grade citric acid, and a 5 lb pail of sodium hydroxide ( food grade Lye)
Haven't been able to find 0-14 or 0-12 ph strips yet though. Might have to order them.

My RO in wash cycle with just the lp pump running is able to max out the Flowmeter at 10 gpm so I'm sure it's more but it reaches 50 psi. Is that to high for washing with soap / acid?

[mainline]

Usually for a good end of year cleaning I do a soap wash and rinse with permeate. Then do acid wash and let it sit at least a few days but no more than 30 days. After it has had a chance to sit rinse with permeate or good clean well water no chlorine. Chlorine will kill most membranes. Well water should not have a lot of minerals. If it does not leave stains in your sink you should be ok. Then soap wash and rinse again. After that the membrane will perform like new if it was not totally plugged to start with. Sometimes the 30 day wait with acid is worth it if you don't need your r/o asap.

[Bricklayer]

I remember reading a post here but can't seem to locate it. It detailed what soap cleans out of the membrane and what acid cleans out of the membrane. I'm assuming since this membrane was used with well water that it has a lot of mineral build up in it. I do get a good flow through it so it's not too bad.
The well water at my place is pretty good. No stains in the sinks or toilets. No chlorine and water is not softened at all. Kind of why I want to use this membrane. Just to make permeate if needed from well water.

[BreezyHill]

Go to MES web site. There was a very good pdf on washing membranes and how, what, when, where to use them.

Low flow is what the DOW techs told me is necessary. You don't want to be making any permeate when washing. I only use the supply pump to wash now. Works much better and uses less power.

MY well water is fairly high calcium. We have to do water tests for the greenhouses for fertilizer balancing for different plants. 7.6 was the water ph and from the well at the store it was 6.7. 7 minutes away. Lesson I learned is not all water is equal. $10 test saved us $300 on acid for the mums.

[Bricklayer]

Made 275 gallons of permeate from well water over the last couple of days with the membrane the way it was. Did a 50 gallon permeate rinse at about 50 psi. Warm soap wash at ph of 11. Then a 100 gallon rinse. Acid wash was ph 3. I had to keep adding citric acid every 10 minutes or so because it kept creeping up to ph 5 or so. Finally got it to stabilize at 3. Let it sit overnight and circulated it again for 10 minutes and flushed it out with 50-80 gallons of permeate all at about 50 psi.

I ran permeate through it to test my flows and what I noticed now is when I start lp pump I'm at 50 psi. When I start hp pump now the pressure drops down to 20 psi and the lp pressure switch shuts down system. This is with needle valve wide open. When it was running before this the pressure would actually climb to 55 or so when the hp pump switched on
Is this because I'm running permeate through it?
I changed the filter after all the washing.

[Bricklayer]

Ran the rest of the permeate I had through it changed the filter again and it seems to be back to normal.
Don't really know what a benchmark for this membrane should be on well water. But with the 10-15 gallons I did have left of permeate I ran through at 200 psi with the hp pump on. Got
1.3 gpm permeate
4 gpm concentrate out
Recirc 3 gpm
So basically 7 gpm concentrate to 1.3 gpm permeate at 200 psi
Is that good?