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 Seuss
Error: divide byzero
Registered: 04/27/01
Posts: 23,394
Loc: Caribbean
Last seen: 3 months, 5 days
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 Plumbing problem 
#14974974 - 08/25/11 07:35 AM (1 year, 8 months ago) |
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I've got an odd plumbing problem that I am trying to figure out. The house uses a cistern to hold collected rain water. A shallow water jet pump pulls water from the cistern to provide water to the faucets in the house. It is your basic shallow water well setup, with pump and pressure tank, but with a cistern under the house rather than a water well.
The problem I am having is the pump continues to lose prime, but only when under extreme load. The footvalve is functioning properly, and the suction line remains full of water when prime is lost. The prime isn't lost until the pressure tank completely empties. At that point, the pump will be running around 20psi, but will slowly drop down to around 10psi at which point prime is lost.
To regain prime, all I have to do is unplug the pump, count to ten, and plug it back in.
I've replaced most of the piping on the suction side of the pump, assuming that air was getting into the line and causing loss of prime. However, the problem persisted and I have verified that the suction line remains full of water even when prime is lost.
I tried raising the cutoff pressure from 22psi to 30psi, which seemed to help, but did not fix the issue. The cutoff pressure is around 45psi. When prime is lost, the pump housing is not hot, so this isn't a vapor lock issue.
Again, this only happens when there is a huge load on the system... everybody flushes toilets at the same time with sinks and showers running. It also doesn't happen until the pressure tank completely empties. This problem did not start happening until recently, when the water pump was replaced and the pressure tank was properly charged. Previous to the water pump being replaced, the pressure tank was "running" without any precharge (it was completely full of water). The water pump was replaced with the same model and HP as the previous pump.
I'm starting to suspect a faulty pump, but I wanted to get the opinions of people that know more about this than I do.
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Just another spore in the wind.
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 luvdemshrooms
Two inch dick..but it spins!?
Registered: 11/29/01
Posts: 24,810
Loc: Lost In Space
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Re: Plumbing problem [Re: Seuss]
#14975023 - 08/25/11 08:09 AM (1 year, 8 months ago) |
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I can see only two likely problems.
The impeller isn't pushing hard enough, or the foot valve isn't allowing enough flow.
Perhaps the footvalve is undersized for that pump, or it is not opening fully (sediment keeping check valve from opening all the way). Either could have been previously masked by your old pump not being up to snuff.
Perhaps the water line from the valve to the pump is undersized.
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“In politics, few talents are as richly rewarded as the ability to convince parasites that they are victims. Welfare states on both sides of the Atlantic have discovered that largesse to losers does not reduce their hostility to society, but only increases it. Far from producing gratitude, generosity is seen as an admission of guilt, and the reparations as inadequate compensation for injustices – leading to worsening behavior by the recipients.
Thomas Sowell
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Seuss
Error: divide byzero
Registered: 04/27/01
Posts: 23,394
Loc: Caribbean
Last seen: 3 months, 5 days
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The more I think about this, the more it seems to be one of two problems...
1) suction side is being strangled and not delivering enough water to maintain internal pressure needed inside the pump to maintain prime
2) the pump is defective; either rings are leaking, impeller is damaged/clogged, prime baffle damaged, etc.
The jet pump is a simple design and does not have an internal control valve to regulate back pressure. Prime is lost when back pressure is lost.
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Just another spore in the wind.
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luvdemshrooms
Two inch dick..but it spins!?
Registered: 11/29/01
Posts: 24,810
Loc: Lost In Space
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Re: Plumbing problem [Re: Seuss]
#14975318 - 08/25/11 10:36 AM (1 year, 8 months ago) |
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Which brings us back to either the foot valve, or the pump.
Not knowing the details of your setup, I'd suggest trying a new foot valve first, as the pump/impeller is simplicity in itself.
I guess it boils down to is which is a simpler job.
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“In politics, few talents are as richly rewarded as the ability to convince parasites that they are victims. Welfare states on both sides of the Atlantic have discovered that largesse to losers does not reduce their hostility to society, but only increases it. Far from producing gratitude, generosity is seen as an admission of guilt, and the reparations as inadequate compensation for injustices – leading to worsening behavior by the recipients.
Thomas Sowell
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LunarEclipse
Mr. Dogma Free
Registered: 10/31/04
Posts: 10,660
Loc: The Hand
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As a pumps flow rate increases the NPSH requirements go up. Maybe at higher flow rate your pump cavitated and lost prime that way. Or lost prime due to too small or too long of a suction line which makes the NPSH available drop too much that the pump cavitates and loses prime but only at the higher flow rate. Or maybe you have leaves or a bird stuck in your suction line.
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Don't submit to dogma.
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Prisoner#1
Even Dumber ThanAdvertized!
Registered: 01/22/03
Posts: 168,346
Loc: Pvt. Pubfag NutSuck 
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Re: Plumbing problem [Re: Seuss]
#14985827 - 08/27/11 11:22 AM (1 year, 8 months ago) |
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do you have a check valve or backflow preventer in the system?
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there are 923 words in the english language that do not follow the "I before E"
rule, there are 44 words in the english language that follow the rule. this is
the shit our education funding is paying for and these liberals want more money
for education to keep making students stupid
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luvdemshrooms
Two inch dick..but it spins!?
Registered: 11/29/01
Posts: 24,810
Loc: Lost In Space
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Quote:
Prisoner#1 said:
do you have a check valve or backflow preventer in the system?
In my (admittedly limited) experience, all foot valves have check valves in them. I can think of no reason (other than human error), for there to be a second check valve.
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“In politics, few talents are as richly rewarded as the ability to convince parasites that they are victims. Welfare states on both sides of the Atlantic have discovered that largesse to losers does not reduce their hostility to society, but only increases it. Far from producing gratitude, generosity is seen as an admission of guilt, and the reparations as inadequate compensation for injustices – leading to worsening behavior by the recipients.
Thomas Sowell
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Prisoner#1
Even Dumber ThanAdvertized!
Registered: 01/22/03
Posts: 168,346
Loc: Pvt. Pubfag NutSuck
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it's not uncommon, the reason I'm asking is it's also not uncommon for a
seemingly working foot valve to leak down, if his wasnt replaced with the
pump or the suction line then it could be the source of his problem, a
secondary is just redundancy but should one fail the second is in place to
maintain integrity in the system
--------------------
there are 923 words in the english language that do not follow the "I before E"
rule, there are 44 words in the english language that follow the rule. this is
the shit our education funding is paying for and these liberals want more money
for education to keep making students stupid
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LunarEclipse
Mr. Dogma Free
Registered: 10/31/04
Posts: 10,660
Loc: The Hand
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Quote:
Prisoner#1 said:
it's not uncommon, the reason I'm asking is it's also not uncommon for a
seemingly working foot valve to leak down, if his wasnt replaced with the
pump or the suction line then it could be the source of his problem, a
secondary is just redundancy but should one fail the second is in place to
maintain integrity in the system
A foot valve is a check valve on the suction side. A backflow preventer is a check valve on the discharge side. You should have both. Put one between the pump and the pressure tank otherwise the pressure tank flow wants to go backwards.
And yes the ball in the foot valve may not be sealing or it could be lifting when the flow goes the wrong way if there is no backflow preventer. Man I am good.
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Don't submit to dogma.
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Seuss
Error: divide byzero
Registered: 04/27/01
Posts: 23,394
Loc: Caribbean
Last seen: 3 months, 5 days
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The new foot valve that was put on (before I was called) turned out to be defective. The problem was the foot valve not opening enough, rather than leaking, thus the suction side was being strangled. Once the jet flow pump housing emptied, which happened because there was not enough inflow (and no check valve between the pump and the pressure tank), the pump lost prime. Because the foot valve was still sealing, the suction side piping never lost any water. Simply unplugging the pump, letting water rush from the house piping back into the pump, and plugging in the pump was enough to "reset" the system. Thanks for the help, everybody.
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Just another spore in the wind.
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Prisoner#1
Even Dumber ThanAdvertized!
Registered: 01/22/03
Posts: 168,346
Loc: Pvt. Pubfag NutSuck
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Re: Plumbing problem [Re: Seuss]
#14990397 - 08/28/11 11:44 AM (1 year, 8 months ago) |
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--------------------
there are 923 words in the english language that do not follow the "I before E"
rule, there are 44 words in the english language that follow the rule. this is
the shit our education funding is paying for and these liberals want more money
for education to keep making students stupid
|
LunarEclipse
Mr. Dogma Free
Registered: 10/31/04
Posts: 10,660
Loc: The Hand
|
Re: Plumbing problem [Re: Seuss]
#14992826 - 08/28/11 08:10 PM (1 year, 8 months ago) |
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Quote:
Seuss said:
The new foot valve that was put on (before I was called) turned out to be defective. The problem was the foot valve not opening enough, rather than leaking, thus the suction side was being strangled. Once the jet flow pump housing emptied, which happened because there was not enough inflow (and no check valve between the pump and the pressure tank), the pump lost prime. Because the foot valve was still sealing, the suction side piping never lost any water. Simply unplugging the pump, letting water rush from the house piping back into the pump, and plugging in the pump was enough to "reset" the system. Thanks for the help, everybody.
80% of pump problems are suction related.
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Don't submit to dogma.
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Prisoner#1
Even Dumber ThanAdvertized!
Registered: 01/22/03
Posts: 168,346
Loc: Pvt. Pubfag NutSuck
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I agree 100%, pumps suck
--------------------
there are 923 words in the english language that do not follow the "I before E"
rule, there are 44 words in the english language that follow the rule. this is
the shit our education funding is paying for and these liberals want more money
for education to keep making students stupid
|
LunarEclipse
Mr. Dogma Free
Registered: 10/31/04
Posts: 10,660
Loc: The Hand
|
|
Quote:
Prisoner#1 said:
I agree 100%, pumps suck
I was a technical sales engineer specializing in the application sizing seal selection drive choices and pricing of pumps for several years. Pumps are cool, but the engineers designing the systems or the typical end user were ignorant enough to need lots of help. Or trouble was the other result. If you starve a pump it won't like it. It hates it more than just about any discharge condition short of dead heading a PD pump no relief valve.
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Don't submit to dogma.
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