Fridge Filter Flow Rate

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Summary

Get a handle on how clogged your filter has become by measuring its water-dispenser flow rate now and in the future. It's as simple as measuring how much water your dispenser pours in a given amount of time (60 seconds). Measure your flow rate now, then compare it 6 months from now. And especially measure it just before, and just after, putting in a new filter (if they're the same kind of filter).

Use a digital scale to weigh the water container before (dry) and after the pour. This gives a more precise measure than a graduated cylinder.

This will give you some sort of handle on your rates. I would think that 10% is sort of a minimum of becoming clogged. Values like 20%, 30%, or higher indicate a high degree of clogging. I'm not sure how much the values really matter. Realistically, do we really even need a filter? As in, who cares, if you water supply is clean enough to drink anyway?

But still, there it is: A simple but fairly precise way to measure how clogged your water filter is.

  • Our Samsung frig water dispenser cuts off at 60 seconds, very convenient for measurements.
  • You'll want to do 3-5 measures, because there will always be a little variability.
  • See below for an important note on your house's water pressure.

Details: Frig Filter Water Flow Rate as a measure of whether your filter needs replacing

Our Samsung RF4287HARS refrigerator has a water filter in it. I bought three Samsung DA29-00020B water filters for ~$34 each from FridgeFilters.com. These filters say they are rated for 300 gallons or 6 months. What does this really mean? Is Samsung's "six months" overly cautious, so we'll buy more than we really need?

For one thing, I can say that the filter replacement light comes on pretty much at 190 days, if you have only been using it lightly. So it's pretty clear that, if the "degree of clogging" is being measured, it does not amount to much... if we hardly ever use our frig water or ice, it's pretty much driven by time. Said another way, 6 months is an upper bound, even if you hardly ever use your water or ice dispenser.

I noticed that the directions say that if you have heavy lime in your water, the flow rate may decrease or stop. A light bulb went off - This implies that you can tell how clogged your filter is, by measuring its flow rate.

Because we use our water very little (mainly for guests), I simply let my filter stay in (and I reset the filter light), for two years (8/23/15 to 8/24/17).

Before swapping out the old filter, I did a timing test of its flow rate. In 60 seconds, net 1616 g water came through (~.42 gallons). (Using a simple kitchen scale plus subtracting weight of pitcher.) The Samsung's water spout actually cuts off water after 60 seconds (I guess it's a protective thing), making this pretty easy. But it's simple with the timer on your smartphone, too. (Android's alarm app also has countdown and timer functions. Having a friend handle the timer makes this easier.) In retrospect, I should have done multiple measures of my old filter's flow rate, because there is some inherent variability.)

For the new filter, I "purged" it for 6 minutes (six pitchers' full), as Samsung recommends. During which time you could see an occasional bubble gurgling through. By the last pitcher, no more gurgling.

Then I did five tests of the new filter. It poured 1660.2 ± 65.2 g water (N = five 60-second fills). That's a 2.7% increase in flow rate.

So the new filter has 2.7% higher flow versus the previous filter. Not much clogging on the old one, and that's after two years! These were the exact same type of filter; I bought three in my 7/6/15 order.

For the record, there was some slight variation in when our frig's spout turned off. It cut off at 59 to 60 seconds, with an average of maybe 59.6 seconds. However, even a full second (1/60) is only 1.67% variation. Realistically there could have been a half-second difference in pour times; you'd need to video what you're doing (or something) to get better precision than Eyeball Mark I. But less than 1% still means the 2.7% is above margin of error and probably fairly real.

Also: I recommend taking at least 3 (and probably 6) 60-second fills. There is a considerable amount of variation, so you don't want to only do one pour, because it may have been anomalously low or high. I actually rejected one of my six pours which was a net 1504 g water, because it was so anomalously low.

These measures are not perfect. Not unless you want the hassle of precision timing tests (probably using a video camera), etc.

But I feel that the 60-second pour timing test is pretty simple, and good enough for a fairly reliable quantitative handle on how much clogging your filter has.

Footnote on Water Pressure

I'm sure that your home's water pressure impacts the flow rate. Ordinarily it stays about the same, but it's still good to know you've controlled for it. (And good in and of itself, to be aware of your home's water pressure. Then you can also know if it does change a lot, which can indicate a problem. Or at least confirm that it varies a lot.) For the record, my readings were done at 55 psi.

I looked at a lot of hose-bibb (outside water spigot) water pressure gauges. I recommend the Zenport (Zen-Tek) glycerin-filled LPG100, ~$17 on Amazon.

  • Being glycerin-filled increases accuracy.
  • It only goes to 100, which makes it easier to read and more precise in the range household water should be (40-60 psi). Other gauges typically max at 200 or 300 psi.

One drawback is that it does not come with a hose-mating ring and gasket; the thing on typical garden hoses for screwing it onto the hose bibb. I actually just took mine off another cheap water gauge, this ~$10 Watts gauge. The Watts has a nice high-pressure needle also, but in practice I find these to be iffy... your water pressure always spikes severely when flow is turned off at the bib. This makes it problematic for having any true sense of the highest pressure in your house's system. (You never know if it's a true reading, or due to a local high spike.)

If you get both of these, then you have a main, good one (the Zenport) plus a backup and second opinion one (the Watts). Use a little PTFE/Teflon plumber's tape to seal the connection.

A depiction from FiltersFast.com. A generic pic; I think frig filters go the other way (fresh water into the center,; filtered water moves out from center).

Sub Footnote on WTH is a frig water filter made of?

I had no idea what the inside looked like, so I took a knife to it.

I tried cutting one open with a fresh razor knife, but the plastic side was so thick that this didn't work. Turns out Samsung filters are some 4-5 mm thick of plastic, outside.

Finally I used a jigsaw and it cried Uncle.

It's a super-simple carbon cylinder, hollow down the center. Water under pressure goes down the center and moves through the filter to the outside (or maybe vice-versa; same thing). I have posted a some pictures here; I hope it's clear enough.

Destruction of a Samsung Water Filter DA29-00020B, part 1
Destruction of a Samsung Water Filter DA29-00020B, part 2
Destruction of a Samsung Water Filter DA29-00020B, part 3