Water configuration to save night time pumping

mtjag · December 2017

We have a full time off grid home with a 500' deep well. Currently have a soft start Grundfos 5SQ-410 pump that runs directing into three pressure tanks at 6.6 gallons per minute. It takes just over 13 minutes of running to pressurize the house at 40/60# of pressure. The problem is the well pump comes on at night which really hammers our batteries. The current well pump draws 11.2 amps and shows about 2.5 kw while running. I'm thinking of going to a 1000 gallon cistern with a smaller pressure pump so that it can run at night if needed. I will have the solar to use the well pump during the day to pump into the cistern. By the way, our household uses 230-260 gallons of water per day and our elevation is 10,600'. The questions of have are as follows: 1) what is the smallest pump I can get away with in terms of power usage. Also, if a pump can be wired 115v or 230v, should I wire it 115v to reduce the draw of electricity? I've found a jet pump that is 1/2 hp and is rated at 3.1amps at 115v or 7 amps at 230v, doesn't it make sense to wire it at 115v? That particular jet pump shows it will pump at 13 gpm which would be twice as fast as my well pump and that alone would save some battery power. Would a submersible well pump be better if it has a soft start? Do you have a recommendation for a pump or setup that will reduce my battery usage in the evenings?
Thanks for any info.

Estragon · December 2017

What uses the water overnight?

I use a ~500gal cistern for toilets and lawn service. The cictern is elevated a bit, which gives enough pressure for those uses with gravity alone. It covers the bulk of the night time gallons used, so the pressure tanks (2x33gal) generally last overnight. I pressurize at 30/50, which gives a bit more useful pressure tank capacity IIRC.

A small rv/marine pump would likely handle low-flow faucet/shower use if need be. I have one plumbed into the pressure tank manifold, which I use to put antifreeze in to winterize, and which I can use to pressurize hauled water if need be.

mtjag · December 2017

Estragon said:

What uses the water overnight?

I use a ~500gal cistern for toilets and lawn service. The cictern is elevated a bit, which gives enough pressure for those uses with gravity alone. It covers the bulk of the night time gallons used, so the pressure tanks (2x33gal) generally last overnight. I pressurize at 30/50, which gives a bit more useful pressure tank capacity IIRC.

A small rv/marine pump would likely handle low-flow faucet/shower use if need be. I have one plumbed into the pressure tank manifold, which I use to put antifreeze in to winterize, and which I can use to pressurize hauled water if need be.

The water usage overnight is my mother-in-law so that is not something I can control, though I've tried. So, what pump do you use from your cistern to your pressure tanks?

Estragon · December 2017

My cistern normally supplies low pressure only to toilets etc which use lots of water, but don't need much pressure to fill. If need be, I can fill pressure tanks from cistern using the small 12vdc marine pump, but putting the toilets on the cistern cut the high pressure usage enough that it's not really needed.

Assuming a fair bit of the 500' well depth is fresh air, you should be able to save a fair bit of power by pumping to a cistern when the sun shines. In my case, separating out low-pressure / high volume uses works well, but the MIL thing may make just having a small pump fill the pressure tanks a better choice for you.

mtjag · December 2017

Estragon said:

My cistern normally supplies low pressure only to toilets etc which use lots of water, but don't need much pressure to fill. If need be, I can fill pressure tanks from cistern using the small 12vdc marine pump, but putting the toilets on the cistern cut the high pressure usage enough that it's not really needed.

Assuming a fair bit of the 500' well depth is fresh air, you should be able to save a fair bit of power by pumping to a cistern when the sun shines. In my case, separating out low-pressure / high volume uses works well, but the MIL thing may make just having a small pump fill the pressure tanks a better choice for you.

I agree the best plan at this stage is to find a low amp surface/well,pressure pump. I already have the switch in place as well as the pressure tanks so I just need the best advise on the cistern pump.

mcgivor · December 2017

" I've found a jet pump that is 1/2 hp and is rated at 3.1amps at 115v or 7 amps at 230v, doesn't it make sense to wire it at 115v? "

Are you sure it's not reverse 3.1A at 230V and 7A at 115V, that would make more sense.

mtjag · December 2017

mcgivor said:

" I've found a jet pump that is 1/2 hp and is rated at 3.1amps at 115v or 7 amps at 230v, doesn't it make sense to wire it at 115v? "

Are you sure it's not reverse 3.1A at 230V and 7A at 115V, that would make more sense.

Yes, it is reversed...sorry for the confusion. I've not found anything better at this point.

mcgivor · December 2017

Pumping to a cistern/tank makes sense, I pump to a 1000 gallon holding tank and use a 100W Hitachi on demand pump for house pressure The main submersible pump is controlled by a float switch, for level and a sun switch to prevent the pump running in anything less than maximum sun. The tank will last a week of normal use if needed, the well pump is 1 Hp 230V 4A but my static water level is < 20 feet, takes 30 minutes to fill, pumping from depth uses more energy, naturally. The on demand pump could actually be used directly on the well but water is used for irrigation at times, hense the larger pump.

mike95490 · December 2017

Do you have a hill that you could put a elevated tank on, and get 20 psi to run overnight ?

mtjag · December 2017

mcgivor said:

Pumping to a cistern/tank makes sense, I pump to a 1000 gallon holding tank and use a 100W Hitachi on demand pump for house pressure The main submersible pump is controlled by a float switch, for level and a sun switch to prevent the pump running in anything less than maximum sun. The tank will last a week of normal use if needed, the well pump is 1 Hp 230V 4A but my static water level is < 20 feet, takes 30 minutes to fill, pumping from depth uses more energy, naturally. The on demand pump could actually be used directly on the well but water is used for irrigation at times, hence the larger pump.

What is the model number of your 100W Hitachi and where did you buy it? That would work without the pressure tanks since it's on demand and might be what I'm looking for if it's enough. Do you know what psi it is capable of and will it supply a two story house?

mcgivor · December 2017

Make and model in link, not available in all locations,but not sure where you are located.
https://www.hitachiconsumer.com/home/others/products/for-home/home-appliances/water-pump/water-pump-product-page/wt-p100gx2

mtjag · December 2017

mcgivor said:

Make and model in link, not available in all locations,but not sure where you are located.
https://www.hitachiconsumer.com/home/others/products/for-home/home-appliances/water-pump/water-pump-product-page/wt-p100gx2

It doesn't appear to be offered in the US. Do you have yours wired DC and if so are you by passing the inverter?

mtjag · December 2017

Does anyone here use the Grundfos Scala 2 for their pressure pump after pumping into a cistern?

mtjag · December 2017

Does anyone know where I can purchase a Hitachi Wm-P400GX pressure pump on the internet. Apparently, they don't sell them here in the US.

nameunavailable · January 2018

I run a Sears shallow well pump at 220v straight out of my 500 gallon poly tank which in turn is float switched to a variable speed grunfos (Don't recall model or draw) from the well. Have a 12v to 230 European inverter, and returned to US type 220v with neutral by introducing a 230 shuko to two 120v outlet transformer. All is good.

jonr · January 2018

A large pressure tank would be easier and use no energy at night.

Water configuration to save night time pumping

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