Dish soap won't kill mold.

Get something like iodophor.

I had issues with carbon deposits in my water tank and boiler feed lines from one of those cheap BWT water pitchers - if you poured water out before it was done filtering, carbon would dump out through the top of the filter and into the water tank. That's what it looks like to me, but it sounds like you're using a considerably higher end system than I was.

I took out the hose and cleaned it thoroughly inside out, also the water tank as well. i used a hose brush to clean the inside of the hose and with chemicals. i'll keep an eye on this and hopefully it wont happen again.

never had anything like this before.

That appears to be a classic mold infection.

The tubing should be replaced. That type of "tygon" laboratory (silicon) tubing is perfectly acceptable and actually preferable since it is transparent and you can see what's on the inner wall. I would buy a new piece so you start with a "clean" baseline. You can clean the old stuff but you will not get it free of residual mold.

Mold will grow in most any stagnant liquid. Change the water in your reservoir frequently. Washing the tank with soap and water on a regular schedule will slow down any growth and the transfer of spores from the water in the tank to the tubing. I don't like to use stronger cleaning chemicals as you will never get to a sterile environment anyway. This should be a chronic maintenance issue.

Hi,

Mold is another form/word bacteria and it's tough to pin point where it came from.

Could be bacteria in water.. water gets slightly warmed up as it's close to a warmer environment (the machine).. a bit of air in hose.. water which may have something in it and it's starts. Also, are you using the machine daily or is water at times sitting for days?.

Replace hose.. boil the heck out of the metal fitting, clean the plastic tank very well with warm water and good dish soap and rub your fingers in the inside of the water tank... see if you feel any slimy smoothness on walls.. wash all off with fingers over and over.. let all dry and repeat.

What frankly concerns me now is whether you have mold in machine leading up to boiler.

The OP stores the water in jars before he uses it. This is a likely place to pickup spores and or bacteria. If those jars and lids aren't sterilized all kinds of "stuff" could make it into the water and create a nice science experiment.

There's your answer

That could be it, thanks for pointing this out.
I do store them and sometimes for 2-3 days.

I will stop doing that and will fill the water straight from the filtration system only when needed.

Any idea where can I get a replacement hose? I thoroughly cleaned the one I have, but want to replace it just in case.

La Marzocco uses a PVC hose for the water inlet. I can't remember the exact size, but I believe it is 5mm ID. The LM part number is T.3.003. It is not expensive at all to get the OEM part if you can find a distributor near you.

You can measure the OD of the metal tube and go just a tad smaller than that if you want to try finding an alternate hose. The PVC doesn't stretch nearly as much as silicone/Tygon, but it needs to fit tight on the metal tubes to avoid sucking air.

Cheers!

- Jake