I have a 1 horsepower water pump and 42 gallon pressure tank connected to the water company and house. Where am I supposed to insert the 3 pcs of 20" slim filters shown below. Should it before the pump, between the pump and pressure tank, or after the pressure tank? Here is the problem of each.

If I insert it before the pump. What if the filters clog from rusts (there are many rusts and sediments in my metal pipe at house). Then the pump can suffer cavitations causing destruction of the impeller.

If I insert it between pump and tank, it can produce high discharge cavitation too if filter clogs and this can destroy the pump impeller.

If i put it after the tank. This can produce pressure loss defeating the purpose of the pressure tank.

Where is whole house sediment filters usually placed?

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You ask some good questions, I would ask if the filter is rated to be on the output side of the pump. I normally install filters after the pump to reduce cavitation at the pump.

I install a string filter first after the pump to dampen the pump fluctuations some filters can be damaged so a string filter or porous ceramic that can be cleaned are my first. then to the more sensitive charcoal and other filters. Keep in mind even on a city water system that is chlorinated that string filters can still start growing things if not changed out regularly a well water system with no treatment will need more frequent changes. The other filters are usually based on the water quality and volume. 1 home we added a mechanical water meter inline that counted gallons as the owner requested this to get maximum usage of the filters without going beyond the MFG recommendations. Depending on water quality, well vs city the filter life varies.

the last thing I have installed is a UV treatment. I would caution don’t go with the cheapest system without verifying the lamp replacement cost. Some of the less expensive systems to purchase have 2-3x the cost of replacement so in some cases a more expensive UV purchase up front can be much cheaper by year 3.

  • I already have reverse osmosis filters for drinking. So I will install purely 20" slim sediment filters only with 20, 10 and 5 micron rating, without any carbon or ceramic filters since we don't have these ceramic of that size available locally. You didn't mention a pressure tank. My 3 housings are rated at 100 psi. And it's 20" slim housing (not big blue). If I put it after the pressure tank with 30 to 50 psi pressure switch. How many pressure drop would the 3 housings and sediment filters introduce? What do you think? Thanks.
    – Jtl
    Sep 26 '20 at 20:21
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    With the filter prior to the tank any sediment is removed and that extends the life of the bladder in the pressure tank. As far as pressure drop it is not observed if the pressure switch is in the tank as long as your pump can push the pressure, most of the pumps I have installed can push at least 80 psi and some 100+ so with the pressure switch set at 50-30 you should see no difference in the home the tank pressure should stay at 50 dropping down to 30 as it is now with the filters prior to the tank. The reason to have them prior to the tank keeps it clean and no Pressure drop at the tap.
    – Ed Beal
    Sep 26 '20 at 20:43
  • But if the filters are between pump and pressure tank. And the filters clog. Then won't it form cavitation in the discharge line? I read that when the outlput is blocked. It is just as bad as cavitation at the inlet as it can destroy the pump. This is my pump spec. imagizer.imageshack.com/img923/1775/OBepHi.jpg up to what psi do you think it is? It has no pump curve or other data i can find.
    – Jtl
    Sep 26 '20 at 21:54
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    If you look at it like that any time the pressure increases the pump will cavitate. By having filters prior to the tank the sediment and grit , rust is prevented from getting to the bladder and wearing it out earlier. Cavitation would be worse on the suction side and if you put the filters after the pressure tank there will be a pressure drop when the filters start plugging up having them prior really stops wear on the bladder, eliminates pressure drop.
    – Ed Beal
    Sep 27 '20 at 17:59

On a house that does not have a boost pump, I would install filters as the first thing after the in-house isolation valve.

If you are using a boost pump then it is better to put the filters just downstream of the pump. This is primarily for cavitation reasons (discussed below). Putting before the pressure tank and pressure switch gives a bit better surge flow to users, and a constant pressure regardless of filter loading, and like Ed Beal mentioned, doesn't fill your pressure tank with sediment.

If you put the filters upstream of the pump it can cause cavitation because the water pressure goes below NPSH. If you put them on the discharge the pump will not cause cavitation. In either case a completely plugged filter will cause "dead-head" or a zero flow condition that can overheat and destroy the pump.

Filters should be sized not only for the anticipated flow, but also for the sediment loading. There are vortex sand filters that can be installed upstream of wound filters that can increase the solids removal. Typically a differential pressure gauge is installed across the filters and they are replaced when a certain differential pressure is met.

Typically sediment collects at a fairly constant rate so you will see a reduction in water flow signalling you to replace the filters before it causes any issues with the pump. If sediment is spontaneous, like from rattling rusty pipes etc, and you are worried about the pump dead-heading you can install a pressure relief valve between the discharge of the pump and the intake that will allow it to recirculate in such an event.

  • Thanks so the sediment filter location is settled, between tank and pump. But here is the complication. The house has old GI pipes that are already rusty so even if I put rust sediment filters before the tank. I'd still have rusts in all my faucets and shower. So I plan to only use the main pump on the kitchen and 1 room wit new pipes.. d rest wil use d water before the main pump. But I'm afraid d rest wil suddenly lack water while pump is running, see this direct question at diy.stackexchange.com/questions/204366/…
    – Jtl
    Sep 29 '20 at 2:36
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    Yes, it is possible that the boost pump will starve the other users. I would recommend putting all users downstream of the boost pump. The pump certainly wont add rust, so connecting down stream of the pump will be no worse from a sediment standpoint. If your pipes are really that bad you could put a filter at each user (in addition or instead of the whole house filter). Your pressure tank should be plumbed into the bottom so it will chase 90% of the sediment back out of itself. I would focus on water quality at the point of use rather than worrying about life span of the pressure tank.
    – ericnutsch
    Sep 29 '20 at 3:10
  • I just spent over an hour trying a 20" slim filter with a 20micron sediment filter and a small mini pump at my restroom. Well it will be a good idea to put sediment filter right at the user point of use. But i can only use 1 instead of 3 in series as shown in the picture above. Anyway what micron of sediment filter do you think can filter rusts? Is 20 micron enough or must one use 5 micron sediment filter? I can only use one. Tnx.
    – Jtl
    Sep 29 '20 at 7:59
  • The rust particle size is very dependent upon the source and the corrosion chemistry involved; no way to know. The filter should be fairly easy to replace. Just start with 5 micron and if it plugs too quickly for your budget, step up a size.
    – ericnutsch
    Sep 29 '20 at 8:04
  • Im this youtube video I was testing out my minpump and 20 micron 20" slim filter youtube.com/watch?v=XnNLY5BGDsk&feature=youtu.be in the wall faucet, it's 1/2" size but the flexible hose is just 1/4". I measured the output as 8 liter/ minute without pump on & 11.2 liter / minute (about 3 gallon/minute) pump on. I just want to ask if the sound is indicative of cavitation? I was comparing using showerhead and just letting it out without any orifice to understand the difference between suction and pushing. Is there another term for pushing where the showerhead can avoid cavitation?
    – Jtl
    Sep 29 '20 at 9:02

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