is our pump dying? can we fix it?

[moray]

Hello everyone,

About a year ago, we were having some problems with our pump:
http://www.terrylove.com/forums/showthread.php?t=14716

In brief, we live on a steep hill and have a Sta-Rite multi-stage jet pump to boost the water pressure from the street (HMSF Series - 1.5 HP).

Hooked up to the pump are 4 Flotec pressure tanks (One FP7135 - 320 Gallons, Three FP7130's - 220 Gallons).

Here are some pictures:
http://headworld.net/pictures/water1.jpg
http://headworld.net/pictures/water2.jpg
http://headworld.net/pictures/water3.jpg
http://headworld.net/pictures/water4.jpg

The water is used both for the house and for a fire sprinkler system.

Last week, we noticed that the pump was running for a really long time and the pressure was stuck at 40psi. I think that the pressure switch was set to 40/60 at the time.

We cut the power to the tank, and called a pump/well guy who diagnosed it as a bad/dying pump and temporarily reset the pressure switch to 20/40. He recommended replacing it with a 1.5 HP Gould pump.

The pump is currently eking along at 20/40, but is a little noisier than usual.

We have a one-month baby at home, so we have been using a lot more water than usual. Babies generate a lot of laundry!

My questions are:

Does it seem like the pump is really dying, or is it possible that something else is afoot and it can be repaired (e.g. partially clogged jet, damaged impeller)?

If the pump IS dying, what's the ideal thing to replace it with? Should we rethink the whole configuration while we have the opportunity? Would a CSV make sense?

Below are some relevant snippets from the previous thread that have gotten me thinking, but I know very little about pumps and would really appreciate any suggestions. Many thanks in advance!!

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"Your pump is misapplied. You plugged the return hole in the front of the pump. This hole is meant to be used in conjunction with a shallow well jet in your application. A 1/2hp jet pump would have worked better and used much less electricity."

"The pump you have if used properly would have a jet bolted on the front of it. With the jet adding more pressure to what you have now, you could be looking at possibly100 psi. You can add that to the incoming pressure for total pressure. I don't think you would be needing that kind of boost. A shallow well jet pump 1/2hp for instance would pump up to ten gallons per minute and add up to 60 psi to your existing pressure. So that might be the better way to go. The Sta-Rite pump you have is overly expensive and has a motor that will fit ONLY that pump. All other pumps on the market use one of two popular motors that are far less expensive when replacement is necessary. As a matter of fact, the 1/2hp jet would be less expensive than the motor for the Sta-Rite."

"Even though bigger than need be, it's a fine pump (one of the best) so if the electric bill isn't too bad, just wait for it to go bad. I said it's a fine pump and it is, but it's not fun to work on. It's probably one of the hardest pumps to work on. So replacement after failure would be the best thing in my opinion."

"And those large powered valves, are they pressure regulators? Why a regulator on the city main when there's little flow and a pressure relief valve on the outlet of the pump?

"Why a Pressure Regular on the pump outlet up the wall before the pressure tanks? No drains on the tanks or entire system plumbing!!"

"Yes it sounds like it was damaged by the long run time, if it won't make the pressure it did before, either the impeller is damaged or the jet is partially clogged."

“I don't know that the stored water is for fire fighting, there's barely enough stored for a family of four for an evening's water use! It seems more a rube goldberg system due to low water flow up the hill than fire fighting. Atmospheric storage instead of pressurized would be a much better system for both needs. If there is a fire, and no power because it is an electrical caused fire, how is this water used for fire fighting?”

"Everything else is looking pretty bizarre, especially what looks to be the pump output running through a pressure relief valve! Thats a first."

"As it is he may have a melted impeller etc. which is very affordable to replace."

[valveman]

You may be able to just replace the impeller if it is worn. It might also be just some debris in the jet assembly.

When those tanks go bad, and they will, you can replace them with a CSV and a little 4.4 gallon tank. This will save you tons of money and space, while giving you better pressure in the house. You will need to get the pump working properly either way.

[moray]

Thanks valveman for the reply and the photo!! The CSV and small tank definitely look like a much more reasonable system than all of those huge pressure tanks, and I'm sure we'll want to do that as soon as those tanks fail.

Are either of the pump problems that you suggested DIY repairs? (As you can probably tell from my post, I don't know much about pumps!)

Given the local rate for on-site repairs ($100-150 trip charge, plus $100-150/hr labor), I wonder if it would be more cost effective just to swap out the pump with a new one?

We can get a new Goulds pump for $500-600, so it would probably cost $1000 installed.

Thanks again for your help!

[moray]

BTW, would a CSV be compatible with our current pressure tanks? If so, we'd like to install one of those now, regardless of what we do with the pump (repair or replace).

The water is used for the house as well as a fire sprinkler system.

Thanks again!!

[Mr.Nice_Guy]

Holy cow; that's a lot of 'tank'.
So you are boosting the city pressure (lowered from elevation) to 60psi - I'm assuming the tanks and pump are in the house? (or same elevation as house?) If you are worried about the fire/safety sprinkler system... unless you have an insanely large storage tank, You're probably talking 5 min of 'pressurized' water until the tanks run dry; at which point you'll be at the mercy of the city pressure.
So ignoring the storage tanks, you would have a couple options...

1) Size a variable speed pump to handle the high flow demand of the sprinkler system. This way, it will only use the energy it needs to provide a constant pressure to the house. (speeds up/down according to demand - and KW ($$) usage drops as a cube of the speed)

2)If you go with the CSV, this would be the cheaper option. If you size it to supply the high flow demand of the sprinkler system, then that pump's going to be using more HP($$) at the low flow demands of normal usage because it's always spinning at 60Hz. The HP drop is linear for low flows as opposed to exponential - and you'll only needing the emergency flow during an emergency. (1% of the time)

In either case... get rid of the tanks. The chances of them 'Coming in Handy' at the right time: [lose city pressure during the day] or [lose electricity when you have a fire] are nil.

[valveman]

Moray, yes you can install the CSV even with the big tanks. Just need to set the CSV at 58 PSI when used with a 40/60 pressure switch, so it doesn't take too long to fill the pressure tanks.

Mr. Nice Guy
I can tell you must have been to one of the big pump or motor company schools where they made you drink their Cool-Aid. What they didn't tell you is that a variable speed pump also loses head or pressure exponentially (by the square of the speed), so saving energy by the cube of the speed is a mote point. There is so little difference in the energy consumption between a CSV and a VFD, that the fact that the VFD continues to use power even when the pump is off, usually means the VFD uses more energy than the CSV. In any case you will never save enough energy to ever pay the extra expense of the VFD. This is especially true because the VFD system has an average life of about 3 years, compared to 15 years for the CSV system.

This system with a jet pump is a good example of why VFD's do not save energy. That pump can only be slowed down by 7% and still maintain 60 PSI. That means that even if you can save energy by the cube of the speed, that 1.5 HP pump can only be slowed to a 1.2 HP load. Using a CSV, the linear drop in horse power will reduce the 1.5 HP to about .8 HP load.

VFD's are really old technology. Anything that can be done with a VFD, will work much better with a CSV..

[Mr.Nice_Guy]

... What they didn't tell you is that a variable speed pump also loses head or pressure exponentially (by the square of the speed), so saving energy by the cube of the speed is a mote point.

That IS the whole point... where do you think the energy savings comes from? It all depends upon what the high flow of the sprinkler system is and also what the pressure boost is compared to the static head. 20gpm? 50gpm? 100gpm? (I only brought this up because there was a 980 gallon pressure tank on the system. So I'm assuming a decent flow)You are correct only if the duty point is on the lower end of the flow spectrum.

And at 75mA and $0.10/kwhr ==> 1 hr of vfd is about $.000825. I'd say THAT is a moot point .

[valveman]

It all depends upon what the high flow of the sprinkler system is and also what the pressure boost is compared to the static head.

And at 75mA and $0.10/kwhr ==> 1 hr of vfd is about $.000825. I'd say THAT is a moot point .

Thanks Mr. Nice Guy. I am glad we agree. The only way a VFD can save energy is if you can reduce the head or pressure required. Kind of hard to do when you are trying to maintain a “constant pressure”. You would be surprised how much energy a VFD uses by itself. 20 watts to hundreds of watts, depending on the size of the VFD. In stand-by mode, a VFD also uses as much energy as computers and TVs. Now do you want to talk about harmonics, stray voltage, reflective waves, voltage spikes, resonance frequencies, bearing currents, cooling, and all the other problems associated with variable speed drives? BTW, welcome to the forum. We appreciate the feed back.