GPM requirements for a whole house water filter

[Zot]

Hi,

I want to install a whole house water filter. Using UPC calculations for wsfu's from this table http://www.toolbase.org/Docs/Subsyst...umbingcode.pdf

I conclude that I need roughly 22-23 GPM to fully service my house. However, most whole house filters I find advertise 8 GPM as their high flow systems. I have 5 family members and it is conceivable (actually, it happens all the time!) that the dishwasher, laundry, shower and toilet flushing is occuring at the same time. The few systems I can find with 20-25 GPM are expensive, and then I have read that high flow rates minimizes contact with filter material, reducing effective removal of chlorine, chloramines and other contaminants. Any guidelines would be much appreciated as to realistic flow rates I should be looking for to support our needs (as well as the real story on contaminant removal!)

Zot

[Bob NH]

Filter systems should be DESIGNED to meet a set of requirements.

Filters typically remove suspended solids; dirt. Devices that are intended to remove dissolved materials are technically not filters, but those devices may be installed in filter-type housings or systems.

There are differences of opinion among those posting to this board about whether to use a backwashable filter or a replaceable filter. I am in the replaceable filter camp for a couple of reasons.
1. They can remove smaller particles and the cartridges are produced with the quality control to ensure that they will perform as advertised.
2. Systems are less expensive to install and in the cases that I work with have the lowest cost per 1000 gallons of water for systems that meet the EPA requirements that my systems must meet.

Backwashable filters can remove 50 micron particles without pretreatment of the water. Municipal systems use backwashable filters to remove particles down to the range of 1 or 2 microns by using approved chemicals to cause the small particles to agglomerate to filterable size. Swimming pool filters work in a similar manner but the chemicals are not always approved for use in potable water. Operators of water treatment plants use process controls and laboratory analysis to make sure the filters are working. There was an outbreak of cryptosporidiosis in Milwaukee in the '90s that killed more than 20 people when the chemical pretreatment process got out of control. That is not a system for homeowner use.

I install systems for small public water supplies that typically use 1000 to 20,000 gallons per day, and flow rates from 5 up to about 70 gallons per minute. The "Big Blue" size housings, which use a 4.5" diameter x 20" long filter can be connected in parallel and are often the most economical for systems in that range. They can be used to remove suspended solids or precipitates, and there are activated carbon cartridges that will remove organics, chlorine, and disinfectant byproducts.

Larger housings such as the Harmsco "whole house" filter housings are more economical when a lot of cartridges are required. Links are provided below.

http://www.harmsco.com/pdf/IP_Calyps...NAL_040904.pdf

http://www.harmsco.com/uploads/pdf/h...ge_catalog.pdf

http://www.harmsco.com/uploads/pdf/w...filtration.pdf

There are ways to reduce the demand on the filter system. One way is to use a pressure tank after the filter to level out the peak flows from toilets and household faucets. If you check your water meter to determing the peak flow in typical 15 minute, 30 minute, and 60 minute periods, you would get a good idea of your real demand requirements. You should monitor actual use; not a special case resulting from, "OK everybody, flush all the toilets and turn on all the showers."

From your comments about chlorine, I infer that you are on a municipal supply. That could eliminate the need for removing sediment and you probably want to remove treatment chemicals.

Determine requirements (flow and what you want to remove), and define what is important to you (capital cost, operating cost, life cycle cost, do-it-yourself of contracted, ????). Then shop for the system that will meet your needs.

[Gary Slusser]

There are differences of opinion among those posting to this board about whether to use a backwashable filter or a replaceable filter. I am in the backwashed filter camp for a couple of reasons.

1. They can remove by mechanical filtering of particulates AND/OR oxidize soluble, converting them to particulate matter and then filter them out.

2. A correctly sized, based on the SFR (service flow rating) required, a backwashable filter will over it life cost (purchase price + operational cost) less than any system made up of disposable or reusable cartridge or bag filters. In the households that I work with, they consistently produce the best quality water while having a totally automatic operation. They also require the least maintenance for the households/businesses that want their water quality to consistently meet the EPA requirements.

My backwashable filters can remove down to 5 micron particles without pretreatment of the water; these filters are standalone or the pretreatment for other equipment. My backwashable filters do not require the use of approved or non-approved chemicals to filter down to 5 microns. My customers of water treatment equipment automatically know if their water quality is correct or not but they can have their water tested if they choose. All the equipment I sell is made of US FDA/NSF approved for potable water use materials and I have treated surface waters and brought it up to meet EPA standards.

I sell residential sized turbidity, acid neutralization, iron, H2S and carbon filters using a variety of minerals or mixed minerals up to 2.5 cubic feet (the max size is solely dictated by the available water pressure and gpm for successful backwashing of the mineral bed), with flow rates (based on the mineral(s) being used) up to 20 gallons per minute. Rarely does a house require that large a flow rate; usually not more than 12-13 gpm. Unless you follow any of the ridiculous codes, one of which is the subject of this thread... That is one single tank with an automatic time clock control valve. This type filter can be used to remove suspended solids and solubles of all kinds.

Here are some threads concerning backwashable filters and other equipment:

http://www.qualitywaterassociates.co...opic.php?t=276

Then one concerning results.
http://www.watertanks.com/forums/topic.asp?TOPIC_ID=536

[Zot]

Thank you both - you've given me some helpful tips and some interesting reading!

Zot

[vaplumber]

First, avoid the filter if you can. Check into a treatment system. If you use a filter, or with a treatment system even, match the flow to your well capacity, or if on city water, match the flow rate to your supply pipe size.

[Gary Slusser]

Hi,

I want to install a whole house water filter. Using UPC calculations for wsfu's from this table http://www.toolbase.org/Docs/Subsyst...umbingcode.pdf

I conclude that I need roughly 22-23 GPM to fully service my house. However, most whole house filters I find advertise 8 GPM as their high flow systems. I have 5 family members and it is conceivable (actually, it happens all the time!) that the dishwasher, laundry, shower and toilet flushing is occuring at the same time. The few systems I can find with 20-25 GPM are expensive, and then I have read that high flow rates minimizes contact with filter material, reducing effective removal of chlorine, chloramines and other contaminants. Any guidelines would be much appreciated as to realistic flow rates I should be looking for to support our needs (as well as the real story on contaminant removal!)

Zot

Cost is the purchase price plus the maintenance costs over the life of the equipment. The most expensive choice is to buy the wrong size based on purchase price and then deal with the problems and additional maintenance that decision causes you. Not smart comes to mind.

The codes establish the SFR (service flow rating) as if you have all the water on in the house at once. My prospective customers laugh at that and thereby I don't size to the code, people will not buy that large a softener or filter BUT... the reason for the code is valid. If you exceed the SFR gpm of the equipment's mineral or resin, it can not remove all of whatever it is supposed to.

As to what SFR gpm you need, that depends on how many bathrooms and independent water users in the household AND if you have a large tub, multiple person showers or multiple shower heads or shower wall type showers etc..

"Whole house" filters meaning disposable cartridge types, aren't meant to be used as POE (point of entry). They were designed for POU(use) applications for say a washing machine, soda dispenser etc.. And the vast majority of the people that have one, don't need it. Especially if the water is always clear. There is little sense in filtering invisible 'dirt' unless you have a water softener or backwashed/regenerated filter with a control valve that gags/chokes on the slightest build up of 'sediment'. Nothing else in the house will do that.

I do not suggest whole house removal of chlorine or chloramines. Use a drinking water filter at the kitchen sink or a filter on the hower head.

Vaplumber, can you explain "match the flow to your well capacity, or if on city water, match the flow rate to your supply pipe size."? IMO neither gives you the correct gpm but maybe I'm wrong although I don't think so.

[vaplumber]

I do not suggest whole house removal of chlorine or chloramines. Use a drinking water filter at the kitchen sink or a filter on the hower head.

Vaplumber, can you explain "match the flow to your well capacity, or if on city water, match the flow rate to your supply pipe size."? IMO neither gives you the correct gpm but maybe I'm wrong although I don't think so.

Actually, you explained this yourself. With all points of water useage in operation, if you are using 15 gpm, then this is the flow you need. If however your water supply is only capable of providing 12 gpm to the house, then there is no use in going above this. If you have 4 fixtures that are capable of producing a flow of 5 gpm per fixture for a total of 20 gpm, but your supply is only capable of sending 12 gpm into the house for whatever reason, whether it be well capacity or entry line size restrictions, then there is no use in going way over the 12 gpm rating for filtration. I only say this because there are many houses here that have only a 3/4 iron supply line from the street, and I can imagine after 30-40 years of use, this 3/4 supply has become more like 1/2 inch line. I have a chart here some where that lists pipe size to length to water pressure ratios and gives the max flow rate of the pipe based on these parameters. My son does most of the filter and treatment work here, and he sizes everything to the maximum possible flow rate that the system can push into the building.

[Gary Slusser]

Actually, you explained this yourself. With all points of water useage in operation, if you are using 15 gpm, then this is the flow you need.

A.... if all points of water usage in operation are using 15 gpm, the system can't be supplying only 12 gpm. Which alone proves my point but...

If however your water supply is only capable of providing 12 gpm to the house, then there is no use in going above this.

Well yes that's true talking about SFR gpm only but... there is if the larger size softener may be required for salt efficiency.

I have a chart here some where that lists pipe size to length to water pressure ratios and gives the max flow rate of the pipe based on these parameters. My son does most of the filter and treatment work here, and he sizes everything to the maximum possible flow rate that the system can push into the building.

From a chart I have here somewhere and my web site: "the flow rate from a 100' of 3/4" pipe at 50 psi is 17.5 gpm, for 1", it is 37 gpm. At 30 psi, 3/4" is 14 gpm and 1" is 28 gpm. Of course you will not get that much flow if you have the same ID pipe because your plumbing includes tees and elbows and valves which cause pressure losses and the fixture risers are much smaller ID than the pipe feeding them.".

I don't size based on the maximum possible flow, I size based on how the family uses water and the number and type of bathrooms in the house; in other words more toward the actual usage.

As to well water systems... ALL submersible pumps can (must) deliver more water than the household actually uses OR the house would be out of water at high usage times.

And the same applies to the city water customer. I've never heard of a well or city user complaining about running out of water unless the well pump is shot or has quit or the city shut off their water.

So, my point is to not size water treatment to the output (recovery rate) gpm of the well OR the pump gpm rating or the ID size of the water service line. Either use the fixture count methodology (which I do not suggest either) or the actual peak demand gpm the household uses. Otherwise the equipment will be too small SFR gpm wise and not be capable of removing all of the hardness etc. it is supposed to, or way over sized and probably will cause channeling of the bed.

[vaplumber]

A.... if all points of water usage in operation are using 15 gpm, the system can't be supplying only 12 gpm. Which alone proves my point but...
>>>True but not true. If your well can only pump 12gpm, then 12gpm is all you will ever get.

From a chart I have here somewhere and my web site: "the flow rate from a 100' of 3/4" pipe at 50 psi is 17.5 gpm, for 1", it is 37 gpm. At 30 psi, 3/4" is 14 gpm and 1" is 28 gpm.
>>>Sorry about the "from a chart I have here somewhere" comment. I have to refer to charts sometimes. Side affect of a massive heart attack and 2 major strokes. What kind of piping are you referring to? Not all pipes have the same inside diameter. Many are reffered to by OD and not by ID.

As to well water systems... ALL submersible pumps can (must) deliver more water than the household actually uses OR the house would be out of water at high usage times.
>>>Not true at all. Regulations require pump to be sized strictly to well depth and recovery rate, and pressure tank and piping to be sized in accordance. No more and no less. And of corse the family will never use more water than they can get into the house. The family will either have to get use to not having 15gpm from a 12gpm well, or else do something diff.

way over sized and probably will cause channeling of the bed.
>>>Ive had many complaint calls for undersized systems, but have never witnessed channeling in the bed from too large unit, even in spite of all the warnings. By the way, from several remarks in your post, my opinions concern filtration systems, (alternate materials) and not water softeners. Softeners have to be sized almost perfectly, but I thought that he was asking about filtering the water, not softening it. There are so many young couples around here who are adding both to their family and to their home, so I almost always oversize. Never had a complaint as of yet with the systems that we install, although have had calls requesting us to add to and increase these systems.

[Gary Slusser]

(Gary said)A.... if all points of water usage in operation are using 15 gpm, the system can't be supplying only 12 gpm. Which alone proves my point but...
>>>True but not true. If your well can only pump 12gpm, then 12gpm is all you will ever get.

You need to look up some pump curve charts. Even a 10 gpm 1/2 hp sub will pump more than 12 gpm. I've provided one here below.

I've never seen a pump sized too small to provide the max gpm the building requires plus some reserve gpm. I've never installed one either. But the figures were yours; using 15 gpm and the 12 gpm was from the well.

(Gary said)From a chart I have here somewhere and my web site: "the flow rate from a 100' of 3/4" pipe at 50 psi is 17.5 gpm, for 1", it is 37 gpm. At 30 psi, 3/4" is 14 gpm and 1" is 28 gpm.
>>>Sorry about the "from a chart I have here somewhere" comment. I have to refer to charts sometimes. Side affect of a massive heart attack and 2 major strokes. What kind of piping are you referring to? Not all pipes have the same inside diameter. Many are reffered to by OD and not by ID.

My memory isn't all that good either but, I've been using charts since my USAF days, '60-'65, in nuclear weapons maintenance, along with being an electronics troubleshooter and becoming a private pilot, among other things back in the day. That was a chart about CTS copper tubing I think.

(Gary said)As to well water systems... ALL submersible pumps can (must) deliver more water than the household actually uses OR the house would be out of water at high usage times.
>>>Not true at all. Regulations require pump to be sized strictly to well depth and recovery rate, and pressure tank and piping to be sized in accordance. No more and no less. And of corse the family will never use more water than they can get into the house. The family will either have to get use to not having 15gpm from a 12gpm well, or else do something diff.

"Not true at all"!! IS TOO!! lol There are codes as to the minimum psi a water system must provide. It doesn't matter how many fixtures are in the house/building, the system has to provide the minimum psi if one or all of them are turned on. In your statement, the pressure would not be but a few psi and well below the minimum.

A 12 gpm well means the recovery rate gpm of the well. It has next to nothing to do with the volume of water provided to the house/building or the total volume the pump and plumbing can deliver to the house/building. The total 'head' is based on the water level in the well though.

You can size a pump by the 'pumping level'. That is where the recovery rate equals the rate the water is being pumped out of the well AND where the water level in the well stabilizes, meaning the pump is removing as much water as is running into it (recovery rate) AND the pump has drawn down the well of all storage. A 6" well has 1.47 gal/foot of water. Usually you would set the pump 10-15' below that water level as measured from the surface. That is only one way of sizing a pump and I don't suggest it due to the possibility of dry periods causing the water table to fall from time to time, creating a dry well condition.

What "Regulations" are you talking about? I've never heard of any regulations on sizing a submersible pump anywhere in the US or Canada, and I pay close attention to these things. You can size a pump for the pumping level of the well as described above or 10-20' off the bottom of the well. That applies to rock bore wells, not cased and screened types which you would usually size the pump from the highest producing screened area.

(Gary said) way over sized and probably will cause channeling of the bed.
>>>Ive had many complaint calls for undersized systems, but have never witnessed channeling in the bed from too large unit, even in spite of all the warnings. By the way, from several remarks in your post, my opinions concern filtration systems, (alternate materials) and not water softeners. Softeners have to be sized almost perfectly, but I thought that he was asking about filtering the water, not softening it. There are so many young couples around here who are adding both to their family and to their home, so I almost always oversize. Never had a complaint as of yet with the systems that we install, although have had calls requesting us to add to and increase these systems.

I think that if your filters or softeners were sized correctly for the building they are meant to serve, you wouldn't be asked to add to or increase them.

All non-backwashed (upflow), automatically backwashed or regenerated filters and all softeners (both manual and automatic) have a SFR (service flow rating) gpm that is established by the mineral or resin manufacturers.

[vaplumber]

You need to look up some pump curve charts. Even a 10 gpm 1/2 hp sub will pump more than 12 gpm. I've provided one here below.
>>>Very true. What I was referring to concerns placing a 20gpm pump into a well that recovers at, lets say 15gpm. Im sure that you have witnessed some of the people out there who actually believe this will work, and it will...for a very short time

I've never seen a pump sized too small to provide the max gpm the building requires plus some reserve gpm. I've never installed one either. But the figures were yours; using 15 gpm and the 12 gpm was from the well
>>>You're right about the figures. I blew this one! Lol! There are several wells around here that are sized too small, but there is nothing that can be done. There are several even around 5gpm, and the owners dont want to mess with elaborate reservoirs and such, so they must live with it

What "Regulations" are you talking about? I've never heard of any regulations on sizing a submersible pump anywhere in the US or Canada, and I pay close attention to these things. You can size a pump for the pumping level of the well as described above or 10-20' off the bottom of the well.
>>>In new construction here, we must provide a recovery rate on the well right after drilling, and a maximum pumping rate after the pump is installed. The maximum pumping rate is required to be right at, or within 10% less than the recovery rate, measured at the very start of the test when the well is full. If it pumps over the recovery rate at the very start of the test, we have to downsize. Even if a house has 2 kitchens and 3 bathrooms, we are not allowed to overpump the well. If it is only capable of supplying 10gpm to the house, then that's what they get, and with low pressure at times. Speaking of which, you are spot on about the water pressure drop, and for recovery rate and pumping rate, I have seen many wells which the owners were not allowed to place in service without a storage tank set up. We have one house here with a 2000 gallon cistern, and 2 low yield wells feeding the cistern in alternate cycles. This is the way that it really should be done with a small yeild well, but many people feel that if it passes inspection without a reservoir, then forget adding one.

Usually you would set the pump 10-15' below that water level as measured from the surface. That is only one way of sizing a pump and I don't suggest it due to the possibility of dry periods causing the water table to fall from time to time, creating a dry well condition.
>>>We are required to set the pump no more than 25 feet from the bottom, and no closer than 15 feet to the bottom, although I have never had an inspector check this.

I think that if your filters or softeners were sized correctly for the building they are meant to serve, you wouldn't be asked to add to or increase them.
>>>This is why I tend to oversize. I have had calls to replace many which were sized to average useage, (by both other companies, and some installed by me to what a previous family requested) and I now install to the maximum possible useage, meaning plenty of leeway for growing families and added or remodeled home additions. I was very reluctant to try oversizing this much at first, but after doing a few and not having problems, I started doing them this way. By the way my son does most of the water treatment work, so I am not familiar with any changes in design, or regulations by manufacturers within about the last 3 years.

[vaplumber]

Carried over from pumps and wells forum

You need a constant pressure, say 40 psi and a flow meter on a 1" line to come up with accurate figures, and you should run that water for some time before taking the measurement. Vaplumber, this goes to the other thread we have ongoing about well output.
>>>Gary I done some reading over my notebooks, and some thinking, and I realize that I have been deleting the pressure from my figures. This is one that I cant believe that I did! Lol!! I will however stand by my statement about sub pumps being sized to the well, and not to the house. Even if the total household has the capability of using 15gpm, and the well only will recover at, say, 10 gpm, then we are not allowed to pump the well above 10 gpm. This is what I meant by regulations. This is what the county requires, and we have to log everything very carefully before the county will give the green light to place the well in service. The driller has to provide a log with the well recovery after one hour of pumping, and the final measured rate must be taken with a stabilized static water level. When we install a pumping system, we are allowed to fall to 10% below the recovery rate, but we can not attempt to pump above that rate whatsoever at all. We follow the pump curves closely, but I have found that many of the curve charts are rated conservitily, which complicates the 10% rule. When we provide our final maximum pumping log, we have to take the flow measurement at the very start of the test when the well static water level is high, and this is when we can not exceede the 10gpm flow on a 10gpm recovery well. This is when throttling (wrong word I know) the pump sometimes comes in handy, although this is not a very good idea. I do realize that as the seasonal water table rises and falls, the well recovery rate will change, but they want us to follow this rule at the time of installation and testing. I am not familiar with the rule in other states, or even in other counties within this state. This is just what they tell us that we must do. They do not care about pressure here, which I myself disagree with. If every fixture in the house is open, and the water pressure is only 5 psi, as long as that well is not pumping more than 10gpm, then the county is happy. If all you have is a single room cabin with a single cold water fixture on a washing bowl, and no bath or other fixtures what so ever, we still are not allowed to install a pump system that pumps less than 10% below recovery on that 10gpm well. Gary, I hope that you did not take offense to my challenges to your post. As I have said in the past, I am learning alot from all of you, and I hope that somewhere here someone has learned at least a small amount from me. These are the reasons that I am here.