What causes sediment to settle on glasses and cups in the dishwasher?
If there is sand or sand-like sediment in the dishwasher and it did not arrive there from any item(s) washed in it prior, it arrived via the water supply. This means it came from either the water supply or from the pipes in the house, if the pipes are corroded old steel or iron pipes. If it came from the water supply and/or the piping system, it will also be in the washing machine and all other water using appliances. Check the aerators on the sink faucets and inside the toilet tank. If any of those locations have the same problem, it may be the water supply or the water piping system. In those cases, other major problems exist, which will not resolve the dishwasher problems.