Girard Tankless Filter

[Lakeswoman]

We winterized our GreyHawk 31DS today. Removing the filter is required so that the anti-freeze does not go through it.

Two questions:-

What color is that filter supposed to be? Ours is sort of brownish, which makes me think it has sediment, after just one 3-day trip this fall. The unit is new, BTW.

Also, can we use a second filter, making 2 in-line filters altogether, at the water inlet as well as the one at the tankless heater?

TIA.