manually fill up a bottle of water and check how many L per minute u get or buy a meter gauge to test pressure

I recently had the filter media replaced on my Alphamax filter. Whatever media it is, it is still sand, so over time, despite backwash, it's going to accumulate dirt. The media that was removed from my filter didn't look clean, and there seems to be some algae as well. 

I did contact Alphamax as well, and they quoted an exorbitant RM800 to change the media, and proposed that I buy a new filter instead.

Since the stainless steel casing was still in good condition, I didn't think it was necessary to change the entire filter.

Actually, the filter is a very simple device; it is essentially a casing, a filter head (with a pipe running to the bottom of the casing), and filter media. If your casing and filter head are still in good condition, only the media needs to be changed.

Reduce the flow from the meter stop cock.

My understanding of pressure regulator is to reduce water flow ...

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I'm confusing with the filter media, from the thread here, I saw a lot ZeoPlus Zeolite, is this a famous brand/type of sand?
I saw some water filter have 5 layer / 7 layer, if using ZeoPlus Zeolite, how many layer will it have?