Sediment debris in faucets and toilet valve

I have a 2014 30DS and have had constant problems with the toilet valve clogging with what appears to sediment debris.

At first I thought it was pvc shavings, but it is not.

When I change the anode rod in the water heater and the same type or sediment was rinsed out.

I understand how this sediment could get into all the faucets that provide hot water,
Sinks, shower, eg.

But how does the sediment get into the flush valve since it is only cold water?

How do I correct the problem?

Thanks in advance