Well pump size verification

[justler]

Hi guys,

I'm spec'ing a Grundfos SQ pump because I need a low startup current and the SQ series offers startup current draw that's the same as the highest operating draw. I'd like to run the pump off a smaller generator and have room for my AC as well which I always got a micro-air easystart for.

I've also got some sediment in the well I'd like to clear up prior to the pump so we were planning on installing a Lakos Sub-K when we swap the pump (I called Lakos as the pump is a 3" and the applications engineer said he hasn't seen it but heard in the field folks shim the boot the Sub-K comes with where it clamps with something so it tightens up - likely 4" rubber coupler that's cut down).

Here are the details on my well:

6" Well diameter
200 ft from ground surface to bottom
40-50ft static water level
~150 ft from static water level to bottom

Current pump is at approximately 175ft (we pulled it up last time due to it sitting on sediment.

Well report I have from about 5 years ago says:

Hour pumped: 3
Pumping Rate: 4GPM
Before Pumping: 34ft
When Pumping: 200ft

From the static water level (40ft) to the highest fixture is approximately 60-70ft vertical. Probably about 100-120ft horizontal (About 60 ft to the well cap from the side of the house and another 60ft to the opposite side of the house). Piping is Black Poly, 1 1/4".

It's cement grouted, no screening (Open Hole).

Looking at a 10GPM (Currently a 10GPM pump in the well). We have 3 Full baths - all with double sinks, two half baths. Two adults, currently one toddler and will be having more kids.

I was thinking of a Grundfos 10SQ07-200. I gave these details to the folks at aqua science and they came back and recommended a 10SQ07-240. Here's what they said:

"I would choose the 10SQ07-240-230 the 200 will not be able to make pressure when the water static level drops down closer to the pump".

Can you guys help me verify if the 240 head pressure unit is the right choice? I tried putting together the TDH calculations but it's been hard for me to work through the documents I've found and specifics around where the water is sitting, vertical height distance to what fixtures, and what exactly is pumping height (in my mind it would change all the time, until you pumped all the water out).

 

[Reach4]

"I would choose the 10SQ07-240-230 the 200 will not be able to make pressure when the water static level drops down closer to the pump".

Can you guys help me verify if the 240 head pressure unit is the right choice?

They are right if you want to be able to suck down to 175 and still generate 60 psi.
So (175 ft lift) + (140 ft =60 psi) = 315 feet of head. On the other hand, your water level may never get down close to 175 ft, so the 200 may be good in practice.

With your high static level you could lift sediment out with an air lift pump. Takes time, and maybe an 8 cfm compressor. There are videos and other info on the web.

With a big engine-driven compressor, you could run air down a 1 inch pipe to the bottom, and blow sediment out like a geyser. It may not need 1 inch pipe, but 1 inch would work. Well Cleaning - YouTube
This was done for a show, but the guy had had his well cleaned this 10 years ago. So not much sediment to be brought up in this cleaning. Nice description of the process.

 

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[justler]

They are right if you want to be able to suck down to 175 and still generate 60 psi.
So (175 ft lift) + (140 ft =60 psi) = 315 feet of head. On the other hand, your water level may never get down close to 175 ft, so the 200 may be good in practice.

With your high static level you could lift sediment out with an air lift pump. Takes time, and maybe an 8 cfm compressor. There are videos and other info on the web.

With a big engine-driven compressor, you could run air down a 1 inch pipe to the bottom, and blow sediment out like a geyser. It may not need 1 inch pipe, but 1 inch would work. Well Cleaning - YouTube

Trying to understand the math.

175ft for the pump depth to top of the well cap for the lift?
140ft is the difference between the pump depth and static water level?

Can you explain your calculations a little more? I guess what would be the downside with going to the 240 over the 200? I don't believe we suck the well down all the way to the bottom, but I suppose we could. Would be nice to have that capability but maybe not at the expense of some other issue.

Pumping the sediment seems like it could be a good idea as well.. Would this work if I don't have a screen? Assuming we're just blasting air down to the bottom and it pushes the sediment up.

 

[Reach4]

140ft is the difference between the pump depth and static water level?

A column of water 140 ft high will have about 60 psi at the bottom. So 60 psi is about 140 ft of head -- actually 138.4, but I round up. So for every foot of height, that is equivalent to 0.433 psi.

https://www.convertunits.com/from/psi/to/feet+of+head is a calculator that can convert either way.

So the pump provides head to climb, and head to produce pressure. They add.

 

[justler]

I'm thinking i'll go with the 240. If i'm reading the chart right with 315ft of head if i'm at the bottom, I'm pumping around 7-8gpm, 12gpm if i'm running and pump down from 50ft static to 100 ft (140+215). This would be the pump running about 6 mins or so (1.5 gallons per foot of 6" water column). My pressure tank is 80 gallons so it's about 23 gallons on a 40/60 switch. Would take a couple minutes to fill that. Does this sound about right?

240 seems the possibly better choice as the best case scenario and worst case scenario are both within it's pump curve. Best case would be 190ft H, worst case 315ft H.

Do I have to account for the elevation from the well cap to the highest fixture as part of my head pressure as well?

 

[Reach4]

240 seems the possibly better choice as the best case scenario and worst case scenario are both within it's pump curve. Best case would be 190ft H, worst case 315ft H.

IMO, if the pump was down to only being able to deliver 2 gpm as the water level approached the pump intake, that would be an advantage, if you could tune things that way. Would you prefer to get 10 gpm until the moment you ran dry? I would not.

Do I have to account for the elevation from the well cap to the highest fixture as part of my head pressure as well?

Elevation from the surface of the water to the pressure switch, if you want to be precise about it. But the surface of the water would be where the pump was if you were about to pump the well dry.

 

[justler]

Ended up going with the 10SQ07-240 and the Lakos Sub-K 5-12gpm unit.

Rented a manual puller wheel from local rental store (for $20) and had my wife walk the poly pipe backwards. Everything went pretty easily. Only problem I had was using the Lakos Sub-K with the 3" pump. Had to get two 3" couplers to take up the space between the Lakos and the pump because the Lakos is meant for a 4" pump. Put a full 3"x3" coupler in the hole, then cut down the second 3" to leave space for the wire channel and take up the rest of the space then put the pump in and clamped it all down.

I swapped out the 25/01 sediment filter last night, ran the water for a bit, took a shower this morning and there's a little bit of sediment in the bottom of the filter case. Excited to see how much of a difference it makes. I know I won't get rid of all of the sediment but i'm hoping for 50% and the large stuff.

Pulled 180ft well pump, swapped barb, installed lakos, water tight heat shrinked connections, pipe taped and electrical taped everything and then went over the piping to make sure everything looked ok and fixed a couple spots where the old electrical tape needed fixed. Total time was about 3 hours.

I did this primarily to get a pump with lower in-rush current. This one hits around 7amp startup with my min-max feature (Don't have multimeter with inrush capability). Old pump was around 28amp. I wanted to add the Lakos to see if I could help the pump with sediment and keep it out of my filters. Well depth measured the same as last time so the sediment doesn't seem to really be building up.

 

[Reach4]

Rented a manual puller wheel from local rental store (for $20)

Cool. Got a picture of that?

A 3 inch flow inducer with a 2-ft tail below the pump would have reduced sediment cheaper.

But the Lakos has some advanced design stuff, so maybe it is worth the premium.

Glad you are getting good results. Thanks for the report.

 

[justler]

Cool. Got a picture of that?

Here's the exact one I rented. Called in on a tuesday to reserve it for the weekend just in case. Told them a whole day rental, ended up being able to return it early for the half day fee.

https://www.rentalsunlimited.com/rental-equipment/well-pump-puller/

"A 3 inch flow inducer with a 2-ft tail below the pump would have reduced sediment cheaper.

It definietly would have reduced it cheaper, 100%. I was hoping with the Lakos I would get just a bit more sediment reduction than an inducer. Unfortunately you can't really tell without doing some testing which would involve pulling the pump and measuring i'm just not interested in doing .

Ordered from a place in Rhode Island that you can find with a google search as well as the pump. Total cost was $1208 for the Lakos ($448), Pump ($740) and Pump puller rental ($20).

Local prices for the pump were much higher unfortunately.

I was worried about running a CSV without a flow inducer/lakos and my level of sediment and am going to watch and see if it is significantly reduce and maybe give one a shot.

 

[Reach4]

Good deal. Next time let your wife pull via a rope to the pitless T-handle and pull the rope by driving a vehicle very slowly.