pump pressure switch location

Hi - I am redoing my water system for my two-and-a-half bath home. The supply is an underground set of cistern tanks making up 5000 gallons. The water level is roughly even with the 1/2 horse shallow-well jet pump in the crawl space. It was what the contractor put in to do the job and it works fine. I had the urge to upgrade however. So I bought this stack of stuff to put in: 20 and 5 micron filters, an additional bladder tank, a Pelican charcoal canister and water softener set, and ozination. I am going to a high quality 3/4 horse jet pump and 1 inch plumbing through all this to deal with the restriction I am adding.

I have two questions really: Should filters be up, or down steam from the bladder tanks? And: Where should the pump pressure-switch be tapped in? I imagine the pump pressure would spike as it hits the upstream side of the 5 micron filter if there were no cushion. Putting the fine filter downstream of the bladder tanks would even water pressure wouldn't it? And putting the sensing switch way at the end of all these parts seems to make sense to me. Please let me know what you think. Thanks.

Pressure switch has to be with the pressure tank. Filters should be after the pressure tank.

I install cartridge filter systems with 5 micron and 1 micron cartridges for systems that are required to have reliable water supplies meeting EPA requirements for public water supplies. If their systems don't work they call me. I get very few calls and they are rarely related to filters. You will have to decide whether the following information is useful to you.

If I just tell you what I think you should do there will be at least 3 people on this forum that will tell me, and tell you, that I am an idiot. Therefore, let's look at what is going to happen.

Typical cartridge filters are designed to operate with as much 30 psi pressure drop across the filter. That is consistent with achieving economic life of the filter.

You have a 20 micron, a 5 micron, and a carbon filter in that order. If you have an average of 15 psi across each of the filters (only HALF of the pressure drop for most economical life) you will have 45 psi pressure drop across the filters. The pressure drop that matters is the pressure drop at maximum flow. It is lower for all other cases.

Pressure drop is approximately proportional to flow, so the pressure drop will be minimal at low flows and the system will deliver almost the pressure that exists in the tank. But as soon as you get in the shower, and someone starts the washing machine or flushes a toilet, you will get a large pressure drop and see a reduction in flow.

The variability of pressure and flow will drive you crazy with that setup.

I use different approaches to solving the pressure drop problem.
1. I install more filter area (more cartridges in parallel) than is recommended by most sellers of filters. That results in a substantial saving in replacement cartridges because there is lower flow per cartridge and therefore less pressure drop for the same system flow.

2. I install filters ahead of the tank and include controls (usually a pressure switch or differential pressure switch) that gives an alarm and shuts off the pump if the pressure drop is exceeded, and a relief valve to protect the filters.

3. In some cases the best solution is to use two tanks with the filter between the two tanks. In your case with 3 filters (20, 5, and carbon) and the extra tank that you mention, you could put the 20 micron before first cistern, the 5 micron after the cistern, and the carbon between the two tanks. The pressure switch would go on the FIRST pressure tank. (Edit - corrected LAST to FIRST)

If you control on pressure at the first tank, then the pressure at the second tank will limit the variation in delivered pressure and the second tank will fill at a lower rate (and less pressure drop) when there is less demand.

I don't know all of the details of the system you describe but you should fully understand the pressure loss situation for all conditions of filter pressure drop and water demand.

Your system with 3 filters is too complex to expect it to work well by just connecting it an plugging it in. If you do that you will not be pleased with the results.

Yea Bob, you're an idiot

Just pulling the leg. i agree with you on this.
That is exactly how we pipe the system.

Hi Folks

Thanks Bob for the thoughtful reply. Good stuff! Allow me to offer this additional info: The water is delivered to our cisterns by a commercial potable-water hauler from the city water-plant. It is usually clear and clean, although just slightly hard. We use 3000 gal every 6-8 weeks. The cisterns are buried and connected together below the yard. The 1 1/4" supply pipe enters the 5 foot crawl space to the suction side of the pump. All the filters and canisters I plan to add are rated as "whole house" and have 1" or better fittings. I don't plan on needing more then 5-8 gallons / minute. Considering your advice and my new found enlightenment, here is what I propose: Put the pump-control pressure-switch at the first bladder tank, the 20 micron filter between the two bladder tanks, double-up with a pair of parallel 5 micron filters after the second tank, and then the carbon and softener etc after that. Perhaps a pressure switch at the end of all this, set at some 20 pounds below the pump switch to sound the alarm that things are backed up. Waddaya think?

What you describe will work fine. I assume from your description that you have a shallow well jet pump to supply the pressure. That limits the risk of overpressurizing the system so you will know to change the filters when you don't get enough flow.

You should have pressure gauges so you can determine the pressure loss across each filter when there is flow. That way you will know which to change.

With a jet pump I would consider controlling on the last tank and let the pump do the best it can to deliver the water. Then put a high pressure alarm on the pump to let you know when to change the filters.

If the pressure swings are too high you could operate the pump and tanks at high pressure and put a regulator on the discharge to the house. When you eventually replace the pump you should select one that delivers high pressure so you can better utilize the available life of the filters.

For example, the J5SH is a 1/2HP high pressure version that could operate in the range of 55 to 70 psi and you could regulate to 35 psi for the house.

Hi Bob

Well that all makes sense to me. Yes it is a jet pump. Will deliver 60 pounds. I will set it up with all filters and softener in between the two bladder tanks. Control switch at last tank, set to 35-40 lbs. Alarm switch on pump set to 60lbs or so. Gauges in front fof first filter, between all, and behind the last filter. We'll see if we need regulation. If I want to tap untreated water for the sill cock, could I pull from line between pump and first bladder tank? I would probably need a check valve after the first tank and before the filters to keep them from being backwashed by the second tank, eh? Thanks for helping out.

You will only have good pressure until the small amount of water in the second tank is depleted. Then you will only be getting the pressure that the filters will let you have. The first tank will be over pressurized when the pump shuts off, which will then over pressurize the second tank after the pump shuts off. If you do not heed the alarm, you will burn up the pump, because the pressure switch is on the second tank.

I would put the filters after the pressure tank/pressure switch, and turn up the pressure high enough to get good pressure through the filters. Then you won't need any "alarms" or the second tank, the pump will be protected. You will then know when the filters are dirty, as you will have low pressure in the house.

tom

Well for Pete Sake, Now I have advise to put filters before, in between, and after the bladder tanks. I think I'll go like this: Pump, 30 micron filter, 2 parallel bladder tanks w/pump pressure-switch set to 60 psi, 2 parallel 5 micron filters, carbon filter, water softener, ozinator, regulator set to 35, house. And then a nice differential pressure gauge mounted in the garage to monitor drop across the whole thing. Thanks you guys for provoking some deep thought.

Keep it simple (KISS)

Both designs of BobNH and Valveman will work but my recommendation is KISS. Simpler is usually less complicated and in the end is usually more dependable. Complicated usually get's scientific engineering involved.

In addition you may want to consider using a Cycle Stop Valve www.cyclestopvalves.com and a double pressurized system using only one pump.

Porky

Porky said:

Both designs of BobNH and Valveman will work but my recommendation is KISS. Simpler is usually less complicated and in the end is usually more dependable. Complicated usually get's scientific engineering involved.

In addition you may want to consider using a Cycle Stop Valve www.cyclestopvalves.com and a double pressurized system using only one pump.

Porky

Click to expand...

I don't know what you are talking about, and if 3 people on this forum had to define it without consulting with each other I expect that there would be 3 different systems.

It sort of sounds like the two-tank system that I described but with a CSV added; but I can't be sure since you haven't described the system. Also, it is not clear to me how a CSV adds to the performance with a shallow well jet pump.

Please explain the configuration of the "double pressurized system" (what goes where, in what order).

1. Where is the CSV?

2. Where are the filters?

3. Where is the pressure switch and what are the settings?

4. Where are the tanks installed in the system?

5. What are the pressures that result during the expected life of the filters?

6. How much filter pressure drop will the "double pressurized system" tolerate?

7. What fraction of the useful pressure drop of the filters can be utilized with the proposed system?

8. What does the CSV do to make it work better than without the CSV?

The original post described using a 1/2 HP jet pump.

What pressure does the "double pressurized system" require and what pump is required for pumping from the cistern?

toolfool said:

Hi - I am redoing my water system for my two-and-a-half bath home. The supply is an underground set of cistern tanks making up 5000 gallons. The water level is roughly even with the 1/2 horse shallow-well jet pump in the crawl space. It was what the contractor put in to do the job and it works fine. I had the urge to upgrade however. So I bought this stack of stuff to put in: 20 and 5 micron filters, an additional bladder tank, a Pelican charcoal canister and water softener set, and ozination. I am going to a high quality 3/4 horse jet pump and 1 inch plumbing through all this to deal with the restriction I am adding.

I have two questions really: Should filters be up, or down steam from the bladder tanks? And: Where should the pump pressure-switch be tapped in? I imagine the pump pressure would spike as it hits the upstream side of the 5 micron filter if there were no cushion. Putting the fine filter downstream of the bladder tanks would even water pressure wouldn't it? And putting the sensing switch way at the end of all these parts seems to make sense to me. Please let me know what you think. Thanks.

Click to expand...

Why would you want to filter water going into a bladder tank, or two of them? There is no good reason to do that. There is no good reason for two bladder
tanks either.

Disposable cartridge filters will require much more maintenance than an automatically backwashed filter but.... why do you need either type filter? Especially when you are going to use carbon, and why are you using it if not to remove chlorine? Is the water coming out of the cisterns dirty?

The softener will not work right when the pressure/gpm flow rate to the softener falls. You say in another reply that you are planning for 5-8 gpm was it? That is too few for most 2.5 bathroom houses and will be if you have any large tubs or showers.

Are you going to use a disposable cartridge after the ozone?

All these disposable cartridges and the way you are going about this adds up to a lot of maintenance and nickels and dimes. And it's ALL in a crawl space!!

Had you called me to buy this stuff, I would have proposed a much simpler system with many fewer parts which would have decreased your maintenance to keeping some salt in the softener's salt tank and keeping the time set correctly on the softener control valve. I would not have proposed ozone due to having to have extremely dry air to make a consistent volume of it and that would be difficult in a crawl space. A correctly sized UV light would be the best choice.

toolfool

Bought the second bladder tank to ease the duty cycle for the pump. In parrallel they will give about 30 gallons under the pressure I want to run. Can not use backwashed filters or backwashed softeners because I am on cistern and water is precious. It is city water and very clean from the sorce. I just want something between me and the hauler trucks. I mispoke about ozone. I really meant to say that it is a UV treater. The crawlspace is generus. It is 5 feet most places and 6.2 feet where all this apparatus will go. Thanks all for your inputs...

OK but.... a backwashed carbon filter would use lees water than an extra normal load of laundry or two extra showers per week and give much better service and flow rate. And the water you pour out of all those disposable filter housings has to be subtracted from that.

And what you should be watching much more than the water trucks is 'stuff' growing in your cisterns.

toolfool

Well thanks for the advice, but stuff is already bought and paid for. We have been using only 27,000 gallons/ per year. Pretty clean so far without any filtering. Cisterns are tight and underground out of the sunlight. But all the filtering and charcoal and UV is just to make sure I am doing all I can to lessen the risk of what they might pump in there.