Background- made 2 x 100 ltr batches back to back and both went into my settling tank last weekend. All made with nice oil-2 stage-naoh-gpw-perfect 45/5 -WBD-bubble and settle. Nothing went wrong and nothing has changed from my usual process-same chemicals,oil......everything! shake up soap test was as perfect as that test can be.
The problem... I usually filter straight down to 1 mic via filter bags into my 60 ltr 'pump station' [barrel with pump and trigger nozzle on wheels] but the filter clogged very quickly.This filter bag had been used for the last lot of bio so I hung it up to drip back into the settling drum and got another [washed] one. I have 4 of these 1 mic bags which I wash and reuse and have been doing this for 5 yrs with no problems.The 2nd bag also clogged quickly as did the 3rd. So I then filtered 50 ltrs through a bed sheet clipped around the top of the pump station, had to replace the sheet 3 times to get the 50 ltrs through.
Tried to then run it through my last clean 1 mic bag filter and that clogged up too.
All 4 filters then went into the washing machine for reuse the next day [which is now today]. Meanwhile, [still yesterday remember]I filtered the 50 ltrs through J clothes which took ages, added 2 litres of rug and took a bottle sample of this for the doorstep sample, I left the fuel in the pump station overnight intending to refilter it the next day [this morning-Sunday]when the washed filters would be nice and dry.
This morning was a hard frost and the doorstep sample was perfect, however, when I tried to refilter, the filter clogged quickly again. I HAD to go out for a 30 mile round trip and the Landy tank was less than empty so I pumped 25 ltrs in, checked the spare filter was still under the seat ,chucked a tow rope in the back and confirmed that a mate would come and rescue me if needed LOL!!
Needless to say,after 10miles the filter starting blocking and I couldn't go faster than 40mph, a quick filter change and all was ok untill I got nearly back home and it started to clog again-its a coolent heated filterhead BTW.
The bio is sparkly clear, the water in the soap test is the same, I thought it was my bag filters best there best but this batch is reluctent to go through bed sheets and J clothes too.
Tis a mystery.....
I'll still be trying to filter this next year at this rate.
HMPE's?

can they be so small that they can't be seen?
I do have some around the side of the settling barrel but I've had loads worse and always take the bio from the center anyway with no problems.