Question for mechanical engineers, (hydraulics), or plumbers

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We built our own house here in the NC mountains at elevation 3200 feet thirty years ago, and I have gravity water coming out of a bold spring above the house.
I have it piped a short distance from the spring head into a 250 gallon tank which is approximately 60 feet higher in elevation than our house, and then a pipe coming from the bottom of the tank down to the house.
I am thinking of putting a whole house filter right where the pipe enters the house.
My question is will a whole house filter cause any change in the pressure if I keep it perfectly clean?

I don't need any comments about freezing, etc. I am just concerned that it might lower the pressure.

Jack L
 
I'm not a mechanical engineer or plumber but I can tell you that all filters cause some degree of reduced flow rate. When all taps are closed pressure will equalize, but when a tap is open yes, there will be a slight loss of pressure downstream of the filter. If my math is correct with a 60 foot drop you'll have a little less than 30PSI so not a lot. One way to lessen the impact is to plumb two filters in parallel. In this way you double the  filter media surface the water can flow through, thereby lessening pressure drop.
 
There won't be any pressure loss if the filter is adequately sized for the flow you expect.  If you use a very fine filter (small micron value), it will need to be physically larger (cross-sectional area) so that the total flow is sufficient for your needs. "Needs" is subjective too - some people are satisfied with a flow rate of 2-3 gpm, while others feel showers are inadequate at that level or that faucets take too long to fill things.

The pressure loss you observe across a filter comes about when the demand on the downstream side exceeds what can flow through the filter.  Open one faucet slightly and everything is probably fine. Open two more, wide open, and pressure probably drops because the demand for water flow cannot be fully met. You need to provide the right combination of filter material and cross-sectional area so that flow meets your needs. You can plan for average demand, or for peak (worst case), depending on your budget.

You can learn alot about filtering and choices at https://www.rvwaterfilterstore.com/ABcs.htm
 
Agree with all.  Properly sized, you should have no problems.

Try the guy at RVfilterstore.  He is great and knows his stuff!!  I just installed a whole RV filter system from him.
 
Is this on a city water or on a well?  If on a well put the filter between the pump and the pressure tank, also use a big filter.

Another factor is how much "Filter" do you need.. Now a "Micron" filter designed to block bacteria and such will cause more pressure loss than a simple charcoal filter for taste/odor control

The Primary filter on my RV is such a filter, it is granulated activated charoal. no loss that I've noticed

((it is a 3" PVC pipe, with a pair of stainless shower drain covers at each end. adapted down to hose fittings.. Filter floss, a pint of charcoal and more filter floss,  all the "Stuffing" is in the fish isle at your favorite pet-supply place  Does what I ant

Drinking water gets a 2nd filter. (Pur).
 
The 30 psi is correct for 60 ft fall. You can always add a pump in series with the filter to restore or increase the pressure.

Ernie
 
Ernie n Tara said:
The 30 psi is correct for 60 ft fall. You can always add a pump in series with the filter to restore or increase the pressure.

I never thought of the addition of a pump, but that brings up a whole new ball game of a pressure switch, wiring, etc and would be way to much. I am trying to keep it simple

Thanks for the idea though

Jack L
 
Just curious - what are you using this water for?  Primary house water supply?  Supplemental water?  I assume the 30 psi is sufficient for your needs.
 
A standard rv water pump is fully self contained with automatic regulation (usually 45 psi), integral check valve, and demand actuated. Probably as easy as installing the filter, or easier,  plus running two 12V wires. The switch is optional but recommended.

Ernie

 
in a previous professional life, I used to spec and design chemical feed systems (tanks, pumps, piping, controls, valves, etc..), so I've got some experience in this area.  We used to use a lot of bag filters, and cartridge filters similar to what you'd use as a whole house sediment filter on up to much larger housings that held multiple cartridges for much higher flow rates

Yes, an filter will be a restriction in the line.... but if sized big enough any losses would be negligible.

For a point of discussion..... it's usually a reduction in flow rate that folks complain about by saying loss of pressure.  It's not the pressure you care about coming out the shower head in your house, it's the flow rate.  60 ft is about 26 psi I believe, static (not flowing)....so yeah, I'd agree..."about 30psi"

Once it gets moving through the pipe, you'll have pressure drops...for each foot of pipe, for each elbow and fitting, for every valve, filter, etc...  The larger the pipe (to a point) the lower the amount of drop, or loss.  For a drop in pressure you see a reduction in rate, and that is what you notice. 

For most everything you can find curve plots published by the manufacturer...... for a given flow rate how much loss should you expect.....Sometimes the data might be presented in table form.
I found one example, a 5 micron filter that gives you a 1psi drop at 8GPM when clean
just as an example for discussion
https://www.aquapurefilters.com/store/product/200023.200015/ap1001-2-pack.html

I'd say the variables you're concerned with is size(how big is the housing, the pipe connections, etc..) AND the level of filtration (are you filtering out bacteria or just the leaves - how small of a micron rating do you need?).

Anyway, you'd need to look at your demands to best figure out how big of a filter you'd need.... just one 2-1/2 GPM shower at a time, or that + some other things?
and you'd need to look at the water quality improvement you need to achieve....do you need a bag filter or even a strainer ahead of the filter to get out big stuff first to protect a finer filter?
 
This discussion can get highly technical, but the solution for something as simple as this is not difficult.  Use a big-ass filter housing coupled with a filter media with a high flow rate.  You probably want 6-12 gallons per minute (gpm) of flow through the filter at [about] 30 psi. Look for a filter mount and media that has those specs. If you get a large filter housing that can handle a good flow, try a low micron (higher density) filter first. If that's too low on volume, you can switch is a less dense (higher micron) filter media.

If you guess wrong on the filter size and the larger micron media isn't enough, you can add a second filter in parallel. It's not hard to plumb a manifold so you can have multiple lines with a filter on each, and then bring those lines back together into a single feed to the house.

You didn't mention what you want to filter out. If its just sand or sediment, a high micron filter is fine. If you are concerned about microorganisms or dissolved chemicals, you probably want something much finer (lower micron).
 
As an ?OLD? (old as in more ways than one) US submarine veteran the weight of water measured in pounds/square inch is 44#/100 ft of depth, or 4.4#/10ft of depth. For a 60ft drop 4.4 x 6 = 26.4 lbs/sq inch. Just think of a dam on a river, the pressure at a depth of 100ft on the face of the dam is 44 lbs/sq inch regardless if the lake is 1 mile long or 50 miles long! Just think- one of the Subs that I was on was on was approximately 525ft long and 33ft in diameter you can do the calculation, what is the total pressure on the hull at test depth?
 
Hey Coxid, hello from another bubblehead. When you get a chance, go to the "general discussion" section, then under "Framily Veterans", tell us a bit about your service.
 
When repiping your water feed system add a valve so you can shut down the system when changing filter as needed. Also..add 2 tees..one upstream from your new filter..and one just downstream from the filter. Simple to see what your pressure differential is. In industrial systems they add a bypass but you probably don't need the extra work/fittings. Let us know how it turns out!
 

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