??? Is my pump beginning to show signs of Failure ???

**tvl** · 03-23-2012, 07:50 PM

I have a question for the pump and well experts:

I replaced our submersible pump back in October 1995 ............. it is used for our sprinkler system and nothing else. It is a 1 HP 3 wire 230 VAC submersible pump. It is a 10 stage pump rated at 11.9 GPM at a depth of 150 feet (our pump is actually hanging 145 feet from the surface).

For the past few years I have been recording the pressure readings for each of our 16 zones. The 16 zones have a range from 9.5 GPM to 10.5 GPM. I have two pressure gauges and both read within 1 PSI of eqch other. Last summer I noticed the pressure reading for each zone had dropped 4 to 5 PSI from previous years. This year at startup, I'm noticing the same thing. I purposely tried to design the system so that each zone would read anywhere between 42 and 48 PSI when running ............... and had accomplished that task. Now the pressures are reading anywhere from 37 to 43 PSI ................. a 5 PSI drop from previous years.

Does this mean the pump is beginning to wear out and become "weak"? Yes, I realize 17 years of service is extremely good, but I don't want to replace a pump for no reason. The well is in a sand stream and I do now I pump a very, very small amount of sand because I find it in the filter periodically. Is this weraing the impellers OR is there something else I should be more concerned with. If the well was being overpumped because "everyone and their brother" seems to be putting in sprinkler systems in our area, wouldn't I notice some "spitting and sputtering" occurring at the sprinkler heads? Everything seems to run quietly with no indication of well failure. I'm just not sure a pump would exhibit signs of wear as our has if it is failing .............. and that is where I need your input!

Thanks so very much!

**LLigetfa** · 03-23-2012, 08:08 PM

How much the pump produces is not based on how deep it is set. It is determined by how far down it is to the water. If the water is at 45 feet, the pump is lifting just 45 feet, not 145, so if the water table is getting lowered, the pump will slow back but will not suck air unless the well runs dry.

**tvl** · 03-24-2012, 06:13 AM

Just to answer the last post ................ the static water level of the well has beeen running about 117 feet. I have measured this on 4 or 5 occasions and it is has always been the same. However, I have not measured the static water level lately ......... it's probably been at least 5 years since the last time I did. On a couple of occasions several years back, I did measure the level with the pump running and found the level would drop only about a foot or two ................ and this was after a couple hours of constant running.

But, back to my issue ............... and a few more thoughts:

1- Our well was put down in 1978. Lately, it seems more and more folks are putting in wells. I do realize there is only so much water available in any given stream and many of these folks may be using water from the same stream I do. However, if I had a water issue and the water level was dropping below the pump intake at times, would I not hear "spitting and sputtering" at the sprinkler heads? Would I not also see the pressure gauge fluctuating or bouncing around when this occurs? The pressure is steady .................. at least when I am observing.

2- As mentioned in my initial post, I do know I pump a very, very small amount of sand. This may be true for all sand wells???? But, over the years would this very fine sand cause the impellers to wear. And would the wear eventually affect the pump so that it can not produce the pressures I am accustomed to seeing?

3- Based on YOUR many years of experience, what is your best guess at what my real issue is? Am I "barking up the right tree"??????

**valveman** · 03-24-2012, 06:28 AM

That is what pumping sand does to pumps.

**Tom Sawyer** · 03-24-2012, 06:56 AM

I have seen pumps with the impellers all but sanded 1/2 way down and the metal so thin it was like aluminum foil. shortly after reaching that point they just sort of implode in there. How much more time does your pump have? Not a clue but I'd be keeping a close eye on it if you are pumping sand. When you replace it, out a sock filter over it next time.

**LLigetfa** · 03-24-2012, 07:11 AM

Ok, so now we know that at one time you had 28 feet of head. Pump output runs on a curve, so if the level dropped 25 feet, it would produce less but still not suck air. The formula is .43 PSI per foot. You need to fix that variable in the equation.

You could also have mineral buildup over 17 years constricting lines. If the well has a screen, it too could be getting mineral buildup. Some wells open up over time. Other wells stop up over time. You also need to fix that variable in the equation.

As for wear, everything wears. The pump wears, but also the sprinkler heads wear. Sand is not the only thing that wears on the parts. The water will as well.

I replaced my 12 year old Goulds 10 GPM pump that slowed down due to wear from all the sand that went through it. Since I also cleaned and developed the well when I dropped a 10 GPM Grundfos in its stead, some of the difference in output has to do with the well development. Some of the difference could be from switching brands.

I understand that a 17 year old pump is a ticking time bomb. It could last another 10 years or die tomorrow. I wonder if pumps made today will last as long.

The pump you buy today won't be the same as the one you bought 17 years ago. You could see +/- 5 PSI difference based on the same specs. If the new pump produces more GPM, the well might not, resulting in no net gain. If you pump at a higher GPM, you might bring up more sand. You might want to engage a pumpman with a TDR sounder to measure the water level under heavy draw before you pull the pump.

Is the 5 PSI drop causing that much of a problem that it warrants pulling the pump? Could you not just adjust one or two sprinklers?

**LLigetfa** · 03-24-2012, 07:20 AM

Originally Posted by tvl

The well is in a sand stream and I do now I pump a very, very small amount of sand because I find it in the filter periodically.

We need to quantify this. In my case, my pump ate so much sand that it stopped the rotor. We're talking bucket fulls. After that, I would remove about 1/4 cup of sand per year from the 100 mesh filter.

**tvl** · 03-24-2012, 03:55 PM

Thanks to all for your replies!!

I did check the current draw today as the pump was running and found the current draw is just as it has been for the past several years ........ 9.0 amps and steady. So, the motor seems to be doing fine.

To answer one of the above replies .............. no, a 5 PSI drop is not causing any problems. But, I know this isn't normal for the pump in use based on my documentation from the past several years. I just know something is happening. Thus my resaon for asking. Just so you all know, the pump doesn't pump very much sand ................ probably a teaspoon every week. This is with a demand of about 24,000 gallons per week. Naturally, there is wear even with this small amount.

It does seem the majority of you folks feel my issue is nothing more than the pump wearing out. I just wanted to make sure there wasn't anything else I should be concerned with. Thanks again!

**valveman** · 03-24-2012, 04:10 PM

When sand wears a pump the amps will be reduced. So I am thinking like LL said, it may just be the sprinkler nozzels that have worn a little. Could be a little of both. Either way reducing the sprinkler nozzle size will bring the pressure back up.

**tvl** · 03-25-2012, 04:40 AM

Originally Posted by LLigetfa

Ok, so now we know that at one time you had 28 feet of head. Pump output runs on a curve, so if the level dropped 25 feet, it would produce less but still not suck air. The formula is .43 PSI per foot. You need to fix that variable in the equation.

You could also have mineral buildup over 17 years constricting lines. If the well has a screen, it too could be getting mineral buildup. Some wells open up over time. Other wells stop up over time. You also need to fix that variable in the equation.

LL, would you be willing to eloborate on the above two items. I'd like to hear a little more and try to understand what is being implied ..... especially the first item. Thanks!!!!!

**LLigetfa** · 03-25-2012, 07:00 AM

The weight of a 1"x1" column of water a foot tall is .43 pounds, so for every additional foot the pump has to lift you may see a .43 PSI drop at the sprinklers. Therefore, a 10 foot drop in the water table could result in 4.3 PSI drop. I say "may" and "could" because there are other factors.

**tvl** · 03-25-2012, 08:45 AM

Thanks!

But this is still confusing. If the pump is always at the same depth, regardless if the water level is one foot above the pump intake or 110 feet above the pump intake, isnt' the pump still pushing or pumping against the same force? ................. not doubting you so much as wanting more information as this could possibly my my real problem. As I stated earlier, it seems everyone is putting in wells nowadays and I'm sure some of these are using the same stream as I am. If anything, it would seem the pump pressure would increase if the water level in the well dropped ............... the pump would now be pushing against a lower column of water which should have less pressure on the pump itself ??????????????????????? I'm very confused!

**valveman** · 03-25-2012, 09:44 AM

Water in water doesn’t weigh anything. So even when a pump is set at 1000 feet, if the water level is 117’, the pump is only lifting from 117’. And for every 2.31’ the pump has to lift, you lose 1 PSI. So if you are losing 5 PSI, your pump may just be lifting from 11.5’ deeper than before.

**LLigetfa** · 03-25-2012, 09:56 AM

Originally Posted by valveman

Water in water doesn’t weigh anything...

The next time you're out on the lake, bring a metal pail and a rope. Sink the pail to the bottom of the lake. The weight of it will remain the same, namely just the weight of the pail and the rope, until the pail breaks the surface. Then and only then will you feel the weight of the water in the pail.

**tvl** · 03-25-2012, 03:28 PM

Thanks Valveman & LL

OK, I get it now! OK, just maybe I was thinking the pump was the issue when it might be the water level is the real culprit. More investigation is warranted.

Question: Our well was dug in 1978 and has been a very, very good well. With more and more folks having well dugs for irrigation, etc., is it safe to say that one should be concerned about "their" stream slowly being over pumped??? Or is there plenty of water beneath the Earth's surface, which is to say it is rare for streams ................. at least a 30 year old stream .............. to go dry???

One post mentioned a TDR sounder. What the heck is this and how does it function?