i have tried using a 5% prewash and without before demething and settling, before sending thru the resin tower

My question which is best practice a prewash, or not if your using purolite resin.

Many thanks

I have tried both methods many times. I have found that doing the 5% prewash with a good 12 hour settle reduces my soap content (pre resin wash) by as much as 40%, thus reducing the amount of cleaning the purolite has to do, thus lengthening the life of the resin. I have always been anti-water, but with the new soap testing methods out there I am finding that my fuel was extremely soapy. This is why I was bent on finding a way to reduce the soap with using as little water as possible. After glycerin drain I heat and aerate to remove methanol also. Removing as much methanol from the fuel will also aid in soap reduction.

This has been the first full year I've used the Purolite PD206 resin in lead/lag configuration and have not used so much as one drop of water in the thousands of litres put through it so far.
I do not settle in the reactor but do so in a separate drum equipped with a standpipe where it settles at least 24 hours,often more. I then purge the transfer line and send it to another drum equipped with a standpipe where the biodiesel only wil be heated to about 160F while circulating until the methanol begins to evaporate. I then turn off the heat and continue circulation but from the standpipe instead of the floor drain until the fuel has cooled. It will then settle out another 24hrs during which time residual glycerine/soaps drop out. Then it goes through the two resin beds to then be finished off through a 2 micron canister type fuel filter by CAT.
The CAT is the quality control mechanism. Last year I was switched from artisian well water to super soft city water and had gobs of soaps and these 2 micron cans would clog up several times a year and I had two inline and both hjad to be replaced. Anyway, I've used the same 2 micron can all this year with no signs of soap clogging.
All that said, I've also had samples GC tested for free and total glycerine and the settled only sample came back a "pass" for total glycerine at .240 and once put through the resin resulted in a pass at .161. My two water washed samples also passed at .109 and .203

HTH