“I think the filter needs to be changed.”

English Lesson: I think the filter needs to be changed.

You have a swimming pool in your yard. The water looks dirty, so you say something to your husband about it.

I think the filter needs to be changed.

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(something) needs to be (done)

Use "___ needs to be ___" to talk about work that someone needs to do:

It needs to be done soon.

English speakers use "be __" to avoid saying exactly who should do something. For example, you might say this this to an employee:

The files in this folder all need to be reviewed.

Instead of this:

You need to review the files in this folder.

The first one sounds softer and less direct.

Or you can say "___ needs to be ___" if you don't know who should be responsible:

That old building needs to be knocked down.

Use "___ doesn't need to be ___" when it's OK not to do something:

No, they don't need to be cooked. You can eat them just like that.

change the filter

A lot of machines use "filters".

For example, an air conditioners has a filter to clean dust out of the air. A car engine has a filter to clean dirt out of the oil. Water purifiers have a filter that cleans the water.

After you use a filter for a while, it gets dirty and stops working as well. When that happens, someone has to "change" the filter. That means replacing the old one with a new one.