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Sharksbaja
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Registered: 9-7-2004
Location: Newport, Mulege B.C.S.
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Lencho is right
The volume factor is only relevant while the system is open and being used. Of course you could overwhelm your pump by have too many lines open and
running.
There is a factory set or recommended air precharge number. It is usually set for a specific drawdown. Ususally set at either 20-40 psi or 40-60psi.
The more air you put in the bladder the larger the drawdown. It's just a big balloon pushing the water out.
Read the literature on the system. It is not paramount to use their stated precharge psi. Which obviously is not what is in your tank.
Empty the tank completely then close outlet.. Charge air bladder(fitting on top of tank) till you have 20-30 psi. Next, start pump it should shut off
at the setting of the pressure switch(which you also can adjust but only if you know what yer doin').
Check drawdown, if not enough repeat or just add a little air at a time till you like what you see.
sidenote: tank bladder get saturated sometimes or develop tiny leaks. It's smart to empty the tank and check that every so often. Especially if the
drawdown keeps creaping up.
Bob, put more air in it.
DON\'T SQUINT! Give yer eyes a break!
Try holding down [control] key and toggle the [+ and -] keys
Viva Mulege!
Nomads\' Sunsets
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Pescador
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Location: Baja California Sur
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Lencho is right, if the tank is not starting with enough pressure then drawdown causes it to start up more frequently. I think Corky is correct when
he tells Bob how to pressure the tank correctly.
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Bajalero
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Location: todos santos/ rcho san diego
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Seems like this subject is going in a few different directions. Hopefully what I have to say doesn't confuse matters more.
A basic pressure system has 3 components. A pump motor, a pressure switch to that pump motor and a bladder tank. For purposes of simplicity , assume
you have a negligible head of water , no air in the system , and all the piping and connections add minimal resistance to what your trying to
accomplish pressure wise.
The bladder tank is there for energy storage and to provide a quantity of water before your pump kicks in so the motor doesn't wear out constantly
cycling every time someone turns on a faucet. Most bladder tanks come "precharged " ,but depending on your pressure requirements this is not
necessarily the proper charge for your system. Most manufacturers recommend a charge of air set to 2psi. under the desired kick in pressure (the low
side). From experience , we usually set the air pressure 3-4 lbs. under the low pressure kick in . So, if you want to run your pressure at say 40 to
70 psi, I would set the bladder tank precharge at 37 psi. This helps prevent rapid cycling of the pressure switch (thus motor) if the differential is
too sensitive . Also, a minimal amount of water hammering can cause rapid cycling but now I'm getting too detailed. The make of the pressure switch
you use will determine how sensitive this setting is.
Pressure switches: a good pressure switch will have 2 adjustments . One , the kick in and kick out pressure are both changed without changing the
spread between the two pressures. The second , changes the differential between the two,ie. - gives more or less of a spread between the two pressures
. In effect if you wanted a more consistent psi. in your system, you would decrease the spread - but then your pump works more to keep a more constant
pressure and not usually a good idea. To take advantage of the bladder tanks potential- within reason of course, you can increase the spread to create
more volume drawdown before the pump cycles again.
Bladder tanks: first off , don't buy a small tank thinking you're going to pressurize it to the limit to get more volume draw down. It doesn't quite
work that way and is not efficient . In fact , the maximum possible draw down of a bladder tank is its total volume minus the volume of the bladder at
a set psi . so the MORE pressure you put in it the LESS the draw down volume . If you have a small house you can get away with a small tank . If you
have a small development like Bob and Susan , it would be more efficient to go with a larger tank to supply many guests at once. Tanks are rated by
gallons tank capacity at a given psi. range. I run a 80 gal. tank and get about 10 gal. drawdown (I think) , at a pressure setting of 70 to 95 psi
before the pump kicks in.
I use a switch from Grainger # 6B446
and a pressure tank simular to Grainger # 4MY63
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Bob and Susan
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see... i didn't even know this stuff...
that link was great...lots of info
i'll be checking the tank tomorrow
this month i learned about beds AND water pressure pumps
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Bob and Susan
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i did the math and i think Bajalero is correct... ... and
i read the entire thing...twice
my drawdown is a little over 5 gallons with the 42 gallon pressure tank...
to me...this subject is interesting stuff for building in a place without services...oh yea...i'm typing this from my garage where i currently
live
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Bob and Susan
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now...
i really need someone to explaine this to me...
i have a 42 gallon pressure pump...
i have 150 feet of 3/4" pipe to pressurize to 45 pounds.
(that's alot of volume of water in a pipe)
wouldn't the pump run less time if it only had 10 feet of 3/4" pipe to pressurize and i used 5 gallons at a time?
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comitan
Ultra Nomad
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Most important item to bring from the states if buying a pressure system here is the pressure switch because the ones I've seen here do not have the
cutoff if your out of water, you have to buy a separate cutoff that costs more. you can tell if the switch has a little arm on the side if has the
cutoff feature.
Strive For The Ideal, But Deal With What\'s Real.
Every day is a new day, better than the day before.(from some song)
Lord, Keep your arm around my shoulder and your hand over my mouth.
“The sincere pursuit of truth requires you to entertain the possibility that everything you believe to be true may in fact be false”
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Bajalero
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Posts: 316
Registered: 11-24-2003
Location: todos santos/ rcho san diego
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| Quote: | Originally posted by comitan
Most important item to bring from the states if buying a pressure system here is the pressure switch because the ones I've seen here do not have the
cutoff if your out of water, you have to buy a separate cutoff that costs more. you can tell if the switch has a little arm on the side if has the
cutoff feature. |
Comitan : when you have a supply tank aka pila, that problem is solved by putting in a reverse float switch that works by cutting the electrical
supply to the motor when the water level is low. The manual cutoff switches are ok if you are always there to monitor the water level. If you run out
of water and your pump motor runs , some of them burn up in a short time running dry
http://www.capump.com/catalog/11-basin-float-switches-and-ac...
part# F5006
Lero
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comitan
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Lero
The switch I'm explaining above came from Grainger and it eliminates the need for the system you describe. When my cistern runs dry the switch turns
the motor off. It is part of the the pressure switch,. It has to have the low pressure cut off. As per below.
wiley
http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml...
[Edited on 4-8-2007 by comitan]
Strive For The Ideal, But Deal With What\'s Real.
Every day is a new day, better than the day before.(from some song)
Lord, Keep your arm around my shoulder and your hand over my mouth.
“The sincere pursuit of truth requires you to entertain the possibility that everything you believe to be true may in fact be false”
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Bajalero
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Posts: 316
Registered: 11-24-2003
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Comitan : that looks like a good alternative.
The commercial style switch I use doesn't come with a low pressure cut off but I think they are better sealed to the elements /bugs and seem to last
much longer.
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Bajalero
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By the way , important
When reading these "how to" articles on residential ,do it yourself etc., keep in mind that there are 2 basic types of air - charged pressure storage
tanks.
1, The bladder tank which is what is most common today and what we are mainly talking about ,
2, - a "stand " tank that has no bladder in it so the air charge you put in it comes in contact with the water you are pressurizing. In these tanks
, as the pump cycles , over time the air charge dissolves into the water . So these bladderless tanks require period maintenance to keep the air
pressure charge at the proper setting so your pump switch detects conditions properly.
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JZ
Select Nomad
Posts: 10561
Registered: 10-3-2003
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| Quote: | Originally posted by Bajalero
The bladder tank is there for energy storage and to provide a quantity of water before your pump kicks in so the motor doesn't wear out constantly
cycling every time someone turns on a faucet. |
I was wondering what the tank was for. I had a pump installed but not a tank separate from the cistern.
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longlegsinlapaz
Super Nomad
Posts: 1685
Registered: 11-18-2005
Location: La Paz
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JZ
With your system, the pump comes on every time there's a demand for water. With a water pressure holding tank, you use less electricity because the
tank fills & allows for a set amount of water usage before the pump comes on to refill the tank. Smaller tanks come on a lot more frequently.
Also...I've discovered, there is a LOT less noise transferred through the concrete to adjacent areas if you mount the tank on a separate slab than the
casa floor! Even with the little rubber "footies" underneath! The only up side would be if someone leaves a hose on, you HEAR it!!
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JZ
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Got it, thanks.
Do you need a cistern to use a pressure pump? I.e. can you use it with water feed from the city?
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David K
Honored Nomad
Posts: 64854
Registered: 8-30-2002
Location: San Diego County
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| Quote: | Originally posted by Bob and Susan
now...
i really need someone to explaine this to me...
i have a 42 gallon pressure pump...
i have 150 feet of 3/4" pipe to pressurize to 45 pounds.
(that's alot of volume of water in a pipe)
wouldn't the pump run less time if it only had 10 feet of 3/4" pipe to pressurize and i used 5 gallons at a time? |
=============================================================
| Quote: | Originally posted by Bob and Susan
david k help me here...
you are the irrigation guy.... |
***************************************************************
Sorry I was not here for you sooner...
I just now quickly read the posts after this one of yours and your second question, too...
Pressure is the force on water and it is created only two ways, by gravity or by a pump.
A 10 foot long pipe and a 100 foot long pipe (on level ground) would require the same 'power' to pressure it up to 45 psi... STATIC (no water
moving)... with a gauge on the pipe to test.
This is because water is NOT compressible (you can not 'squeeze' water to increase pressure). You can only 'push' water with the force of gravity or
the force of a pump.
When water is moving, it is called DYNAMIC and everything except going downhill takes away pressure from the water when it is moving (fittings/ turns,
valves, pipe friction).
The other properties of water (besides pressure) are velocity (the speed of water in feet per second) and volume (the flow of water in gallons per
minute)...
All three are inter-connected... change one and it affects the other two.
A lot of people get velocity and pressure confused... For example, some think by running water through a smaller pipe it will increase the pressure!
The opposite is true since smaller pipe has a greater amount of friction pressure loss than bigger pipe. The water will move FASTER, but will lose
pressure (force) and have reduced flow (gallons).
Most of my personal irrigation business is done on gravity systems (city water, from tanks on hilltops)... so I am not a pump expert.
If you think I can help further, then please ask away!
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Bob and Susan
Elite Nomad
Posts: 8813
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then why when i've use city water and ran a sprinkler line 200 ft the power at the end is nothing but a trickle?
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David K
Honored Nomad
Posts: 64854
Registered: 8-30-2002
Location: San Diego County
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| Quote: | Originally posted by Bob and Susan
then why when i've use city water and ran a sprinkler line 200 ft the power at the end is nothing but a trickle? |
Friction Pressure Loss!
As I said above, except for going downhill, everything else takes pressure away from the water!
As water is moving through a pipe/ hose... every foot pressure is lost, every turn, every valve, everything the water touches takes away pressure.
Going uphill will cause pressure to drop, as well.
You can reduce the amount of loss (lose less pressure) by either using a larger pipe or reducing the flow in the pipe.... like with a lower gallon
device at the end.
You can only gain pressure with a pump or by going downhill.
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Bob and Susan
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"every foot pressure is lost"
so now going back...
if i'm using 150 feet of pipe...
my pump works more than if i was using 10 feet of pipe.
so...
if you are pressuring a house the amount of pipe in the house is important to have constant acceptable pressure
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longlegsinlapaz
Super Nomad
Posts: 1685
Registered: 11-18-2005
Location: La Paz
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| Quote: | Originally posted by JZ
Got it, thanks.
Do you need a cistern to use a pressure pump? I.e. can you use it with water feed from the city? |
If you've got "city water" on a reliable 365-day-a-year basis, you could probably forego a cistern...BUT most places in Baja only turn water on for a
few hours each day, then move to another area & turn it on for a few hours & the reliability of when you'll have water, how much, how much
pressure & how long is very unpredictable. Because of that unpredictability, everyone I know uses either a cistern or smaller tinacos to store
water for use 7 x 24. I'm currently in the beginning phase of new const & in a rental where ALL the outside water is only tied to the city water,
which means I'm dependent on the city water being turned on to water plants & alas, to wash clothes. So all laundry must be done in the morning
& inevitably, when I plan to wash, that's the day they miss turning the water on; the pressure is so low it takes an hour for the washer to
fill....or my all-time favorite; the water is turned off before the full cycle, so I have to bucket water from inside (from the roof tinaco) to
complete the load of laundry! By having your own cistern and water pressure holding tank, you can avoid the hassles of both availability &
dependable pressure 7 x 24.
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David K
Honored Nomad
Posts: 64854
Registered: 8-30-2002
Location: San Diego County
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| Quote: | Originally posted by Bob and Susan
"every foot pressure is lost"
so now going back...
if i'm using 150 feet of pipe...
my pump works more than if i was using 10 feet of pipe.
so...
if you are pressuring a house the amount of pipe in the house is important to have constant acceptable pressure |
Constant pressure... ? Again, water pressure can be measured as dynamic or static...
The pump or pila height will create pressure which you can measure with a gauge. At the same elevation that pressure will be the same everywhere in
the house or property, if the water is static (not moving).
Once you open a faucet, shower, sprinkler system, then the water is dynamic and will lose pressure for every foot it travels, every turn in the pipe
it makes, every valve it goes through.
To have less pressure loss, use a bigger pipe (or flow less water). Otherwise use a pump and set the pressure higher so where you want more pressure,
you will have it.
Pumps I have seen will provide 'X' number of gallons per minute at 'Y' to 'Z' pounds per square inch of pressure.
You need to get the pump that will provide the pressure and flow required at the end of the pipe.
If you measure the pressure with the water static (say it's 43 psi from a pump or pila or city water) and measure it again with the sprinkler sysytem
or whatever running and it drops to 23 psi, you will need a pump that can be raised 20 psi more, to maintain 43 psi with the water running. That means
a pump set at 63 psi (43 static + 20 dynamic pressure loss).
Most every water device has a rating of flow at a pressure... Sprinklers will be rated at so many GPM @ 50 PSI... Shower heads too...
There are tables that tell you how much pressure is lost through various sizes and types of pipes at different flows.
Anytime you have a long run and do not want to lose much pressure when the water travels through it, then size up the pipe. The tables will let you
know what size pipe, so you don't waste money buying too big a pipe or lose pressure by using too small a pipe. You will need to know the estimated
flow (GPM) through the pipe and the distance (FEET) to utilize the tables.
I have them in my book for 1/2" to 2" pipes (PVC sch. 40/ Class 200 and copper type M and L).
[Edited on 4-9-2007 by David K]
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