Good day to you.

Our septic tank is located right infront of our entrance door because it is the only space available for it. Main door facing NW. I hang 5 rods of chimes on it, I sense something is wrong because since occupied this unit, my family members will easily get sick. I would appreciate much if any one could help me.

Btw, the septic tank is buried below earth.

I read some where that walking below wind chime is not good . is it correct?

Thank you.

The septic tank even below ground when in front of your main door is considered as bad in feng shui.
Since your entrance is facing NW, it indicates head, colon, lung and bone issues especially to male occupants.
Although the septic tank is buried under ground, it will still affects the ground chi especially the septic tank is located at the "mouth of chi" of the house.
This is why it is bad to built houses on ground that used to be a garbage dumping site. This is called "luan tao sha".

Get some green plants outside your entrance door, the wood element will help to counteract the earth element which is associated with the septic tank.
Always replace them to healthy ones

Why use 5 rod wind chimes? You will have to remove the 5 rod wind chime because it is the enhacing the bad chi associated with the septic tank esepcially in 2014 when
5 yellow flying star which is located at the NW sector. This star will brings serious misfortune and health problems affecting the male occupants.

I will suggest you put

1. Mechanical music box plus a cup of water or
2. hang 6 old Chinese coins on top of the entrance or
3. 6-rods metal wind chime

The so called walking pass below window chime is not auspicious is just like the saying that walking under a stair or ladder,
which are purely superstitious belief and have nothing to do with authentic Chinese feng shui.

Cheers, Peter