New pump, low pressure issue.

[Pistol Pete]

Good day all,

I have recently installed a Grundfos 15SQ05-110-115v pump and it won't build pressure past 38 psi. which does not allow the 30/50 switch to cut out. If you isolate the pressure tank (there is a valve on it) and isolate the house so that the pump dead ends at the switch/gauge and throw the circuit breaker supplying the pump, the pressure will drop to zero after only a minute or two. I suspect the check valve on the pump is stuck open, which would account for the loss but would a stuck check valve prevent the pressure build up necessary to satisfy the switch in the first place ?

I would think the pump would run until it hit the cut out pressure, shut off, lose pressure, cut in and cycle itself to death if left as is. But it never gets past 38 psi. There is no sound of a leak at the well head (at least above the water mark) The down pipe (one piece tubing) was in good shape when it went back in but I concede a hole below the water line might account for this. Thoughts ?

The well is 136' deep
Static level is 88' from the surface or 48' of water.
121v supply
Pump draws 4.8A when running

Thanks,
Pete

 

[Reach4]

I have recently installed a Grundfos 15SQ05-110-115v pump and it won't build pressure past 38 psi. which does not allow the 30/50 switch to cut out. If you isolate the pressure tank (there is a valve on it) and isolate the house so that the pump dead ends at the switch/gauge and throw the circuit breaker supplying the pump, the pressure will drop to zero after only a minute or two. I suspect the check valve on the pump is stuck open, which would account for the loss but would a stuck check valve prevent the pressure build up necessary to satisfy the switch in the first place ?

No. The held-open check valve would not cause your symptom.

Your symptoms are more like from a hole in the pipe or a leak at the pitless o-ring. If the leak is above the water line and if you have a pitless, you might be able to see or hear the leak if you take the well cap off.

Now I see the problem is the wrong pump.

 

[Sponsor]

 

[Pistol Pete]

There is no leak at the adapter and there is no sound when peering down the well casing. I'm assuming at this point if there is a hole in the pipe, it's below the water surface.

To be clear, if there is no leak, this pump should be able to produce more than 38 psi at 128 feet of head, correct ?

 

[Valveman]

My calculations show a 15SQ05-110 lifting from 88' can only build 36 PSI. You needed the -150 pump or larger. You need to lower the switch setting where the pump can shut off like 10/30 or the pump will melt down from sitting there running and not pumping any water.

 

[Reach4]

I had not paid sufficient attention to the pump choice. The real problem was choosing a cheaper weak 15 gpm 1/2hp pump rather than a strong 5 gpm 1/2 hp pump. If you want 120 volt SQ pump, then you are limited to 1/2 HP. That would call for the 5SQ05-180.

 

[Fitter30]

Where exactly is the pump set in well? Pipe size and type of material?

 

[Valveman]

I think the 10SQ05-200 would be best.

 

[Pistol Pete]

Where exactly is the pump set in well? Pipe size and type of material?

The pump is set 9' from the bottom at 128' from the surface and there is 40' of water (static) above the pump, 1 1/4 poly pipe.

I am limited to 120v due to the back up generator.


I think the 10SQ05-200 would be best.

I cannot locate one on the Grundfos site (or anywhere else for that matter )

 

[Pistol Pete]

I had not paid sufficient attention to the pump choice. The real problem was choosing a cheaper weak 15 gpm 1/2hp pump rather than a strong 5 gpm 1/2 hp pump. If you want 120 volt SQ pump, then you are limited to 1/2 HP. That would call for the 5SQ05-180.

It was far from cheap and yes, you are correct, I chose the wrong pump for this application.

I understand I can compensate for this pump by adjusting the cut in/cut out to 10/30 as Valveman has suggested, but 10 psi sounds like an abysmally low fixture pressure before the pump kicks in.

 

[Valveman]

Sorry, using an old book. Looks like they decided the 200 needed a 3/4HP motor instead and changed at sometime. I still think you need the 200 even though it shows to to 3/4HP number 10SQ07-299. The only 1/2HP would be the 5SQ05-180 and it doesn't pump half the water at like 4 GPM max.

 

[Reach4]

For a house, the 5 gpm pumps pump plenty IMO. If the water static level is higher, they can pump well over 5. For some uses, such as backwashing iron filters, you need more GPM.

On the other hand, if changing pumps, it is not that hard to convert to supply 240 volts into the wires. You are actually allowed to use the white in the power cable as the second hot, but you will need a place in your breaker box for a 2-pole breaker. However you would not be able to use your 120-volt-only generator to power the pump.

 

[Pistol Pete]

For a house, the 5 gpm pumps pump plenty IMO. If the water static level is higher, they can pump well over 5. For some uses, such as backwashing iron filters, you need more GPM.

On the other hand, if changing pumps, it is not that hard to convert to supply 240 volts into the wires. You are actually allowed to use the white in the power cable as the second hot, but you will need a place in your breaker box for a 2-pole breaker. However you would not be able to use your 120-volt-only generator to power the pump.

And that is really the rub. The gen set is an inverter, 3 cylinder diesel in the basement, weighing in at 485lb. It's modest at 7.5kw and has two 120v 30a circuits, but because they are the same phase, there is no 240v. So if I convert the well to 240v, I'll have no back up.

I really appreciate all of the responses and please don't take this next question as refutation of your advice.

That said, I'm kinda pigeon holed into the 115v-1/2hp world of low GPM in my situation. If I went with the 5SQ05-180 (my only real option here) what kind of pressure will I see at the switch ?

 

[Reach4]

And that is really the rub. The gen set is a 3 cylinder diesel inverter in the basement. It's modest at 7.5kw and has two 120v 30a circuits, but because they are the same phase, there is no 240v. So if I convert the well to 240v, I'll have no back up.

Does the generator have a 240 V outlet? I presume not. Normal 240 is single phase. Our normal home system is called "split phase", and can provide both 120 and 240.

That said, I'm kinda pigeon holed into the 115v-1/2hp world of low GPM in my situation. If I went with the 5SQ05-180 (my only real option here) what kind of pressure will I see at the switch ?

Depends on how far down the static water level is. Yours is 88 ft. And lets say the pump is at 127 ft.

The orange circles represent three points on the curve. If you stopped using water, and were filling the pressure tank at 1 GPM, and the water level was 88 ft (green line), you could fill the pressure tank to 75 PSI. However if the water had fallen to 127 ft down, you could only fill the tank to 58 psi. Depending on refill rate of the pump, you might never reach that point.

Delivering 5 gpm, you could deliver 41 psi of pressure if the water was at 88, and only 24 psi if the water was at 127 ft, which would still fill your tub at 5 gpm.

So with a 30/50 psi pressure switch, I think you could do nicely.

Note the negative pressure calculated means that can never be reached, but you could draw 7 gpm with the water at the static level.

​	1 GPM​	5 GPM​	7 GPM​
Total Head ft:​	263​	183​	107​
​	​	​	​
water level ft​	​	​	​
88​	​	​	​
pressure head ft​	175​	95​	19​
pressure head PSI​	75.775​	41.135​	8.227​
​	​	​	​
​	​	​	​
water level ft​	​	​	​
127​	​	​	​
pressure head ft​	-127​	56​	-20​
pressure head PSI​	-54.991​	24.248​	-8.66​

 

[Pistol Pete]

Excellent, thank you so very much.

Now...anybody wanna buy a Grundfos 15SQ05-110-115v ? Only used on Sundays, previously owned by a little old lady from Topeka, real cream puff I tell ya'.

 

[Reach4]

I think Ebay is the place, presuming nobody messages you. With that low head high vol, it could be good for some irrigation but not with sprayers.

Note that the proposed pump will have a 1 inch NPT thread rather than 1.25 inch

 

[Pistol Pete]

Would this A.Y McDonald 6630-255 be a better choice ? Or am I completely misunderstanding what you guys are telling me. I do appreciate your patience, thank you.

 

[Reach4]

That would appear to give more volume and more pressure. It could work with a 40/60 pressure switch. It is a 4-inch pump, and that can be a problem with a 4 inch steel casing as it ages. No problem with a 4 inch PVC casing. If I ever need to swap out the pump on my 4-inch steel well, I expect to use 3 inch SQ.

2-wire 3-inch SW pumps will start on a generator easier. Then a 3-wire 4 inch pump will start on a generator a little easier than a 2-wire 4-inch pump.

A.Y. McDonald | 6630-257

www.aymcdonald.com

This one is running deal:

A.Y.McDonald 24050V3A Stainless Steel Pump Motor & Control Box 7 GPM 0.5 HP 115V 3-Wire Single-Phase

A.Y.McDonald 24050V3A Stainless Steel Pump Motor & Control Box 7 GPM 0.5 HP 115V 3-Wire Single-Phase

www.rcworst.com

 

[Valveman]

Looks like you will be needing 200' to 230' of head, so yes that pump will work. A thousand bucks for a 1/2HP seems really high to me. But I am old. Lol!

 

[Pistol Pete]

The casing is 6" so no issue there.

Looks like you will be needing 200' to 230' of head, so yes that pump will work. A thousand bucks for a 1/2HP seems really high to me. But I am old. Lol!

I put the last pump in 17 years ago and I'm old enough to know I don't want to do another one 17 years from now !

I try not to go out of my way to waste money (failed here, obviously) but I have zero interest in a inexpensive, low quality pump. I did read a thread you guys had from a few years back about the "cheapening" of the pumps by the manufacturers, but we can't control what they offer us for sale, only what we ultimately choose to buy.

That said, all of the AY McDonalds I looked into seem to be at least two weeks out. Any others I should consider, Goulds or Flint and Walling ?

 

[LLigetfa]

Another option would be to use two pumps, with one filling a storage tank and the other pumping from the tank.