Black water runs out in bathtub faucet.

Here is my problem I got. New house 4 years old. Well water. Kinetico softener installed. Whole house filter i believe 10 micron. Electric hot water tank. No odors in water at all. I am noticing on my hot water when we fill our tub in the master bathroom the hot water will run then turn black and then clear up a little then black or gray water out of it. This tub has two water valves with no aerator installed just a fill faucet. When you fill this tub you can really hear the water noise of it running in the house. The other tub / shower combo has a rotary water temp flow valve and we never see any black in it when filling. I'm guessing the master tub flows the water so hard it sucks up sediment from the hot water tank. The black stuff is like a charcoal silt, fine black stuff, sometimes smears black when wiped. How do i stop this? tried to drain hot water tank no change really problem still there. Tried to shock/bleach well no real change noted still black. Then forgot to change the filter after and waited about a month or so later and the filter was solid black. Installed new filter. still black water at times. Checked filter again filter is clear now, but water when filled runs clear the black starts again. Where is this black coming from? Thought anode rod? should i change the types of valves on the tub to slow the water flow? sometimes i think if i fill it slow its better. But definitely if you run it full bore it turns black. Tried to just let it run it slowly got a little better. Then shut off wiped out tub, ran again and it returned black again. Please help. I am very mechanically inclined and have no problems doing what it takes to fix this myself.

I'm going to try closing the shut off valves partially on each hot and cold under the tub like maybe 25%. I will see if this stops the sediment from getting pulled out of the hot water tank.???

What kind of tub is it? I know some hot tubs require a higher flow rate to fill than the standard ones do due to the type of spout they use. Try a 5 micron filter or even a one micron and see if it helps. Also, has it just started or has it been doing it the entire 4 years you've had the home?

It is a jaccuzzi tub with jets. The spigot is not connected to the tub it sits next to it through the tile. So as far as how much water is needed to fill it would only be a matter of how long it takes to fill, not a function. Its a dual valve seperate hot and cold valves with a center spill spigot. I thought about a tighter filter but was afraid I would then be changing that filter way too often due to plugging. At first before we had the softener and the filter it was all ok. But then I had the heating elements fail due to calcium buildup in the hw tank so after that we got the softener. So not always just maybe six months. When I drain the tank and refill it to try and drain the possible stuff out it would flow heavy black out as I purged the air while filling, then go clear. Maybe when I change the filter next time I will go with the smaller micron, although I think they are like 3x the price.

I guess it depends where you buy them and what type they are. The ones I carry are the same across the micron ratings for a meltblown filter. I should back up and say that some of those types of fillers require more VOLUME than standard fillers. I know from being in the biz long enough that at new construction plumbers often times have to run larger lines to certain tub fillers to get them to "work" right. IE: the filler may need more volume to get the water to flow over the spout design properly and not just lazily fall out of it. Those are more high end designs though. Not the standard cylinder type of filler. Hard to explain without linking one for your viewing pleasure.

Yeah I understand what your saying about the water flow. My filler is just a chrome angled neck, nothing fancy. And the flow for us is only how long it will take to fill the tub, no functional reasons. Maybe I will try a finer filter next time. Any good places online to get filters?