This product will take care of the contamination issue if it exists.
Supco
Supco model no. Sud111 or sud115
Cap tube is no. Bc1, BC2, bc3, ETC. BIGGER NUMBER IS LARGER I'D.
They also come with cap tubes already attached. Under ten bucks on eBay every day.
I have learned to install some kind of filter on all my experimental units. Don't ask how. Dirt cheap insurance.