Off Grid Water System

OffGridRory · August 2011

I had previously used this site and corresponding business to set up my small 400w “backup” solar system. Since I found it so helpful, I have returned to inquire about something I have been reading about a lot lately due to our dream of building an off grid house coming to fruition.
I’ve been reading about a topic that I know little to nothing about, so please bear with me if I’m asking questions that are overly simplistic to those more knowledgeable than myself. I’ve been sifting through the other threads in this section trying to find an answer to my exact questions, but to no avail.
Where we’re going to be building our off grid house in Mid-Coast Maine in the next year or so I’ve been looking into how I’m going to supply the house with water. Since I spent all of my energy and time looking into the electrical needs/setup of the future house (which I feel through my last years experience I’ve gained sufficient knowledge) I did not spend ANY time looking into water pumping and storage. I now have gained new appreciation for what planning must go into this and I feel VERY MUCH behind the learning curve here…
The house is essentially going to be a 1000 square foot post and beam type house. Depending on funding when the project starts, I plan on having a full basement dug under the middle of where the house will be (Probably 400sq ft or so)… I wanted to have this so I can have my “man cave” and all my gizmos along with the solar system, generator that will be vented outside, and water system.
I’ve spoken to many of the neighbors that live within a reasonable distance and they have all told me that their wells are about 100’ or not much more (I know this doesn’t necessarily mean anything when it comes to how deep my well will be, but it’s what I’m judging my basics on)
I’d very much like to have a 300gal or more storage in the basement, and because I don’t have the option of having a water tower, I need to have a pressure tank along with it that is capable of pumping pressure to an on-demand hot water heater and the two floors above it… This is where I start getting confused… I’ll just list my questions…

1) Is a 120VAC submerged well pump or a 12v slow pump the best option for me? I like the idea of the slow 12v pump best because I have a separate 12v system with the 400w of solar and 440ah of storage… This will be separate from the bigger system that will run the rest of the house. I’d like to just flip that pump on a couple of times a week when its sunny out to fill my storage tank, but I’ve become concerned after reading about these DC pumps not lasting as long as their AC counterparts??

2) Will a pressure tank that is between the storage tank and the hot water heater need to be fed with positive pressure from the storage tank (Another DC or AC pump) or does it have its own mechanism to draw from the storage tank?

3) How big of a pressure tank is needed for just the two of us living there? No kids in the future, so occasional guests, but normally there will just be two people taking showers every day, once a week running the dishwasher, and the occasional sink being used every day and toilet being flushed. I’ve read conflicting things about small pressure tank vs. large pressure tank.

4) If I were to include a closed loop heat exchange solar hot water tank between the 300gal storage tank and the hot water heater would I need yet another pressure tank and pump from the 300gal storage? I’ve read that most on-demand hot water heaters require a good bit of pressure to run effectively, and furthermore, many do not run properly when fed with pre-heated water…

I’m trying to do this as cheap as possible, but with long-term “livability” in mind… In other words, I don’t want to skimp in the early days and regret it later, instead build it the way it should be and the way I’ll be happy with 10 years from now…

Sorry if my questions are redundant guys… I’ve read the other posts in this section and can’t seem to find suitable answers for my specific questions… I’d really like to do this system myself if possible, but am feeling overwhelmed with no prior knowledge in this area. Thanks in advance!

Rory

mike95490 · August 2011

Re: Off Grid Water System

Good questions, long answers

1) is 300 gal enough ?

2) a pressure tank is about a 30 gal tank, with a 20 gallon balloon of air in it, as you pump water in, it compresses the balloon, which provides 10 gallons of water under pressure, before the pump comes on again.

solar_dave · August 2011

Re: Off Grid Water System

Sounds like maybe you didn't take the sizing of the pumping setup into your solar setup as well. The Coot will be along soon to start querying you on possible pump scenarios I am sure.

Cariboocoot · August 2011

Re: Off Grid Water System

I'd like to say "thank you"; your questions let me know that the decades I've spent dealing with stuff aren't for nowt. I'd hate to think that all that time and effort could have been supplanted by a small brochure available at any government office.

On to the questions!

OffGridRory wrote: »

1) Is a 120VAC submerged well pump or a 12v slow pump the best option for me? I like the idea of the slow 12v pump best because I have a separate 12v system with the 400w of solar and 440ah of storage… This will be separate from the bigger system that will run the rest of the house. I’d like to just flip that pump on a couple of times a week when its sunny out to fill my storage tank, but I’ve become concerned after reading about these DC pumps not lasting as long as their AC counterparts??

Pumps last according to how they're used. The quality of the water will be a bigger determining factor on longevity than whether it's AC or DC. The harder they're worked the shorter the life too. As for being able to use a 12 Volt pump on your existing power system ... Without knowing the details of how much you're trying to pump you can't know how much power it will use and what you'll have to do to supply it.

100' depth is actually a deep well. That is going to take power. Basically you need a certain amount of power to fulfill the requirements of lift, flow, and pressure. You can trade one off for the other, but lift is the base as it is determined by how deep the well has to be. Can't fudge that one! Slower flow or less pressure can be balanced against the lift requirements. For example, pushing the pressure up to 50 psi instead of 40 psi is basically a waste of energy; it takes more power to get that last 10 psi than the first 40, and you don't gain much stored volume or operational improvement by it.

Ordinarily at that well depth you'd have a 3/4 HP submerged 240 VAC pump which would not only provide the lift but pressurize the tank as well. That would not run off a 12 VDC inverter system: too high a power requirement. There are some DC solutions from Grundfos and SunPumps, but they will be $ and no doubt require their own power (some use solar panels directly so they will pump when the sun shines to tore water up).

2) Will a pressure tank that is between the storage tank and the hot water heater need to be fed with positive pressure from the storage tank (Another DC or AC pump) or does it have its own mechanism to draw from the storage tank?

Pressure tank has to be fed pressure: it's a tank with a bladder in it that has air pressure behind it. Normally they have a switch (optional - they don't come that way) on them that turns the pump on at low pressure and off at high. The range is typically 20-40 or 30-50. If you fill from a reservoir tank chances are it won't have enough pressure to charge the system unless elevated. If possible, skip the extra tanks and extra pump: go for a large pressure tank and a pump that can operate on demand to keep it full. The fewer components to a water system the better.

3) How big of a pressure tank is needed for just the two of us living there? No kids in the future, so occasional guests, but normally there will just be two people taking showers every day, once a week running the dishwasher, and the occasional sink being used every day and toilet being flushed. I’ve read conflicting things about small pressure tank vs. large pressure tank.

Small tank = more pump cycles per volume of water used. We have a 60 gallon PT at the cabin. The 1/3 HP centrifugal pump gets run once a day (usually) for 6 minutes to fill it up. Water lasts all day. Bathing and clothes washing will use more. Having the kids there uses way more! The only down side to large pressure tanks are the cost and the ability to fit them in the space available. Regardless of pump type you won't regret having as big a PT as you can manage.

4) If I were to include a closed loop heat exchange solar hot water tank between the 300gal storage tank and the hot water heater would I need yet another pressure tank and pump from the 300gal storage? I’ve read that most on-demand hot water heaters require a good bit of pressure to run effectively, and furthermore, many do not run properly when fed with pre-heated water…

Most on-demand hot water heaters need a whopping 3 psi to work. Mine has a turbo-igniter and will work at 2.5 psi. If you can't supply that then there is something seriously wrong with the system. A solar hot water system may require a pump or it may not: it depends on differences in elevation between the water storage and the solar collector. Some have them all ground-level and let natural convection aided by a check valve or two take care of the circulating. There are so many variations possible here it would take a lot more than 1 post to begin to address them all.

I’m trying to do this as cheap as possible, but with long-term “livability” in mind… In other words, I don’t want to skimp in the early days and regret it later, instead build it the way it should be and the way I’ll be happy with 10 years from now…

Sorry if my questions are redundant guys… I’ve read the other posts in this section and can’t seem to find suitable answers for my specific questions… I’d really like to do this system myself if possible, but am feeling overwhelmed with no prior knowledge in this area. Thanks in advance!

Rory

One day someone is going to say "I'm trying to do this in the most expensive and complex manner possible" - then we'll know he's planning the project for government.

The least expensive way to do anything is to do it right the first time, and that begins with research and planning. So you're already on the right course!

OffGridRory · August 2011

Re: Off Grid Water System

First of all, thank you all for your quick responses

So would the most cost effective and reasonable system require the least parts?

From reading what you wrote it sounds like I shouldn't even bother with a tank dedicated to "storage", instead I should focus on getting the biggest Pressure Tank I can find and use that as my pressure source and storage?

... Lastly, should I wait until the well is dug before deciding on what kind of well pump to get? I'd really prefer to get something that I have to manually turn on/off to fill the tank and NOT have it 240v simply because I prefer to not run anything that demanding in my system... I realize however that a 12v or 24v pump probably wont cut it... To save me some time reading individual operational manuels, what is the recommended maximum depth for a DC pump?

Cariboocoot · August 2011

Re: Off Grid Water System

You really have no choice but to wait until the well is drilled (not likely they'll dig a 100' deep well) to see what the final water depth is and determine how far the run to the house is. If it's a long way off, you have that old Voltage drop problem to contend with.

Our host NAWS actually offers a selection of pumps along the off-grid line here:
http://www.solar-electric.com/sodcwapu.html
You can use that as a starting point to familiarize yourself with some of the options.
Some of them can reach 700' of lift, but there is of course a trade-off on volume.
Consider also that some of these pumps run $2,000+, whereas a standard deep well pump may be about $500. So when you look at the possible solutions you have to include not only the cost of the pump & fittings, but also of supplying power to it. Chances are your existing solar set-up will need expansion to provide enough power for any type of pump, so be prepared for that.

solar_dave · August 2011

Re: Off Grid Water System

I suppose one option might be to have a cistern close to the house and only pump the well when the generator is running. Pump something like a weeks supply all at once. That might help to minimize the need for a larger solar addition.

Cariboocoot · August 2011

Re: Off Grid Water System

You might be surprised. Some of the SunPumps for example can lift from 100' and deliver more than 3 gpm while doing so. Quote one part of the description on the SDS-D-128: "max flow rate will be around 1.25 GPM at 225 feet with 160 watts of panel." Now 1 gpm might not sound like much, but that's 60 gallons in an hour, times hours of good pumping daylight - could be 200+ gallons per day. Big enough PT to store up over-night use and you're looking at a pretty simple install with a couple hundred Watts of panel ($800) and the pump ($800+) and the controller ($400+/-). $2000 total. Now what would it cost to rig up a DC to AC system to supply 240 VAC for a few minutes when needed? Could be a lot more than that, depending on how much power is required. The difference is mainly in allowing the pump to work over hours of time if necessary instead of doing it all in a few minutes.

mike95490 · August 2011

Re: Off Grid Water System

OffGridRory wrote: »

.... To save me some time reading individual operational manuels, what is the recommended maximum depth for a DC pump?

I think grondfos has a 600' model. needs 1KW of pv to pump. $$$$

I like the genset and pump several days worth idea, and use a small pump for household pressure.

OffGridRory · August 2011

Re: Off Grid Water System

Coot, I also see that you and others have the Honda eu2000i generator... I'd also like to stay with a small generator if possible and just use it for recharging batteries during prolonged darkness... Since I'm going to need a generator, would it be more cost effective to fire up the generator and run an AC pump directly off that a couple times a week to fill a storage tank, then use a cheap 12v pump to pump from the storage tank to the pressure tank? I'm just thinking of overall cost effectiveness, the generator is a necessity anyway, so perhaps that eliminates the need for extra panels?...

I guess I'm still a bit confused given the options... I'd prefer to have a system that doesn't require me to run a generator for my water, but instead is set up so I can work with the weather and do most of my pumping when its sunny or windy out when I'm making more power than I'm using... But is that practical?

I like the quote from the manuel that you had coot about 160w of solar running appx. 1GPM... If I were to hook something like that up (Using my battery bank instead of directly off the panels if possible???) and run it directly into the biggest pressure tank I can get my hands on, it would eliminate the need for a large storage tank and extra gizmos that go along with it... That would save some $$$$ and make the system a little simpler... The only thing I would need to watch out for would be having the PT running at night if the battery bank is low...

Would that be a feasible system?

Blackcherry04 · August 2011

Re: Off Grid Water System

A Pressure tank is a middle step that you do not need. Get a 12 V, 5+ GPM Variable speed diaphragm pump. For a $150.00 you'll have a pump that will pump more than you can use and uses 10 amps dc.

You need to get your well in first to have any idea what you need for a lift pump. If you use approx 300 GPD a DC Solar pump will work great for you.

http://www.aquatec.com/aquajet-rves-pumps.html

,

samuel · August 2011

Re: Off Grid Water System

We use a Grundfos 120V soft-start pump in a 125' well without any issues. Our pressure tank is a little larger than usual, but nothing absurd. The tank is set to about 30 psi instead of the usual 50 psi. Overall, that is enough water for 2-3 showers. The toilet seems to trip the pump most often. Our pump runs under 1000W (according to the Xantrex control panel) - but I've complained about the accuracy of the panel so the actual energy consumption could be anywhere from 700 to 1200W in our situation. I'll have to double check with the battery monitor to find out how much the pump actually uses.

120V pumps can go pretty deep, researching what Grundfos has is a good start. I'm pretty sure 200' shouldn't be a problem for a 120V well pump (and still have the ability to pressurize a tank).

Cariboocoot · August 2011

Re: Off Grid Water System

OffGridRory wrote: »

Coot, I also see that you and others have the Honda eu2000i generator... I'd also like to stay with a small generator if possible and just use it for recharging batteries during prolonged darkness... Since I'm going to need a generator, would it be more cost effective to fire up the generator and run an AC pump directly off that a couple times a week to fill a storage tank, then use a cheap 12v pump to pump from the storage tank to the pressure tank? I'm just thinking of overall cost effectiveness, the generator is a necessity anyway, so perhaps that eliminates the need for extra panels?...

A Honda 2000 won't run much of a water pump. Certainly not a 240 VAC deep well one, because they put out 1600 Watts @ 120 VAC. It could be used for supplementing panel production as needed, but would you really want to run the gen every day to get water? The once-in-a-while filling of a reservoir tank is more practical with a gen, but it would need one large enough to refill the capacity quickly as you don't want to be running for a along time or frequently.

Would that be a feasible system?

There's lots of feasible solutions to this situation. Some have been mentioned which may or may not be right for your application. Until you know more about how much you'll be pumping from how far down to how far away, you can't do anything more than speculate. Who knows: you may strike an Artesian well and not need a pump. Or you may come up with a hole in the ground that recovers very slowly. Hopefully whatever water you find won't be hard and smell of sulphur.

mike95490 · August 2011

Re: Off Grid Water System

Or like me, drilled 2 wells, both dry, and ended up having to build a pond to harvest rainwater

OffGridRory · August 2011

Re: Off Grid Water System

I was talking to my friend about this today and he said that what he did was skip the pressure tank alltogether and had some sort of 12v RV apparatus that acted as an on demand pressure system... I'm ignorant to what he was talking about and since he lives on the other side of the country I'm not in a postion to go look at it myself, but he swears that it would be enough pressure to presurize the 2nd floor of a house and in his opinion it would be the most cost effective system and uses very little energy since it only works when you're using something...

He said that he had a 50gal storage tank that he would draw from and would only fill that every 2 or 3 days with a 12v DC pump in a well that was around 90'...

Anyone have any opinions about this??? Seems to contradict what some people have said, but he's been living on a mountain in Wyoming for 10 years 17 miles from the nearest road so I ususally believe what he's telling me simply because he's been living it for a while...

Blackcherry04 · August 2011

Re: Off Grid Water System

OffGridRory wrote: »

I was talking to my friend about this today and he said that what he did was skip the pressure tank alltogether and had some sort of 12v RV apparatus that acted as an on demand pressure system... I'm ignorant to what he was talking about and since he lives on the other side of the country I'm not in a postion to go look at it myself, but he swears that it would be enough pressure to presurize the 2nd floor of a house and in his opinion it would be the most cost effective system and uses very little energy since it only works when you're using something...

He said that he had a 50gal storage tank that he would draw from and would only fill that every 2 or 3 days with a 12v DC pump in a well that was around 90'...

Anyone have any opinions about this??? Seems to contradict what some people have said, but he's been living on a mountain in Wyoming for 10 years 17 miles from the nearest road so I ususally believe what he's telling me simply because he's been living it for a while...

I made you a post # 11. A 5 diaphragm RV type pump has more than enough flow and pressure to deliver anything you need on demand. Back in the day these pumps has 2-4 diaphragms and a on/off pressure switch. they would pulse the water and had other issues. The new pumps are computer controlled and are variable speed with a soft start. They are set to 60 PSI with a transducer instead of a on & off pressure switch. At around $150 they are a deal.

A diaphragm pump is a positive displacement pump, the flow changes little as it pressurizes the water. On the other hand a Centrifugal pump loses flow as the pressure rises. A Centrifugal pump that pumps 20 gpm @ 30 psi may only pump 2 gpm @ 50 psi.

Most all the 12v pump manufactures have licensed the technology from Aquatec and make these pumps , Johnson Pump, Sureflow, Jabsco. Be careful of the Flotec pump, I think it has less flow and 4 diaphragms.

I have removed all the 120/240 stuff I had and replaced them with these pumps.

OffGridRory · August 2011

Re: Off Grid Water System

@Blackcherry... Now I understand more of what you were talking about... My friend didn't know what the diaphram was called... He called it an "RV pressure device".. Now it makes more sense the way you have explained it... I'll look into those and look at their demands etc. I'm REALLY trying to stay away from needing to have an AC anything if possible, and as I said before, do the bulk of my pumping and other needs while its either windy or sunny outside... I realize I will need to fire up the generator, especially here in Maine, during our "Month of Darkness" we seem to have every spring, and other prolonged darkness days, but I'm really trying to keep it simple and 12v if possible... My house will run off a separate system that will probably be 48v, but my existing 12v system (Backup system) is actually bigger than my friend in Wyoming runs his entire house on. With the exception of a larger battery reserve anyway...

Cariboocoot · August 2011

Re: Off Grid Water System

If you can pump and pressurize in one go, that's what you do.
Sometimes it isn't the right solution, and you have to pump to a reservoir: as in high power needed for that one job, so run a generator instead of building $10,000 system that you won't make full use of except occasionally. Then you need a second, lower-power pump to pressurize the household. Some use just an RV pump, some use a pump and pressure tank. Pressure tanks are not that expensive and they do make for a smoother water flow (pump-only systems can pulse significantly, which bothers some people).

But hey - no one has to listen to me. If they do, I might start telling tale of dozens of water systems put in, taken out, repaired, redesigned, upgraded ... it gets boring real fast. I know I'm bored. I think I'll take a nap.

westbranch · September 2011

Re: Off Grid Water System

Just to point out, TIME is on your side.... you can 'build' the final system in stages as long as you know what it will be.
FWIW we have been on a well system for > 32 years, had the well start at 90 feet then 150 feet then 190 feet now at 305 feet for the last 15+ years. We are now on the third submersible pump and have had 2 pressure tanks.

If you are not going to live in the house full time, running a generator is a good alternative to a large PV array and a lot cheaper as you will need the genset to top off your batteries, etc. so if you go that route get one sized to your needs..

I am currently building a new place at the lake and only have a 10 foot deep well with 30 gpm ( gallon per minute) the shallowness is a problem due to freezing in winter, YET I am perplexed as to just which way to go, 12 volt is enticing but there are drawbacks as with 110/220 solutions.

We decided to run a simple summer system to monitor our water use, as this will be a significant change of lifestyle , getting rid of the electric dishwasher as well as some other conveniences. This will initial a small additional expense but the end product will be matched to our needs.

ps go to a good plumbing store with well pump experience and talk to them for their recommendations

HTH
Eric

Cariboocoot · September 2011

Re: Off Grid Water System

Eric;

Freezing level up there isn't any more than 4' even at -40. If the pump and piping are kept below that they should be fine. You may need an insulated well house though. All depends on the design/placement of components.

I'm not up there right now, but curiously am facing the same situation - X2. :roll:

SCharles · September 2011

Re: Off Grid Water System

Others [some of them pro's] have hit the questions pretty well.

I will generally say I've done this as a homeowner. You very definitely wait for final system decisions and design because there is no way for you to predict how deep the well will end up being and how much flow you get, which will likely mean what head you will have. For example, my well drilling hit water at 328 feet, but it is a "flowing well" so the effective head starts at the very top of the well casing. Other wells in my area are not flowing, so who would know?

I have seen advertised pressure tanks with pumps built in. However, they are just that: a normal pressure tank with a pump bolted on. I cannot think of any advantage to this over a simple pressure tank. As other have indicated, my pressure tank is nominally 30 gal. What that means, in our usage here, is that it will provide about 8-10 gallons of water before the pressure drops to the point the pump comes on.

We pump well water up a steep hillside to a cistern which is almost level with the house [steep mountainside: no way to put the cistern above the house to get gravity-pressure]. So we have a Flowlight pump to draw water from the cistern and charge the pressure tank.

Our well pump is operated [turned on] manually. When the cistern levels drops however much, and there is a clear sky and lots of sunlight, I will switch on and fill the cistern. For us this is about once every two or three months.

The pressure pump, on the other hand, is wired with a pressure switch [they are about $10 or a bit more just about anywhere hardware is sold] and comes on depending on the pressure from the pressure tank. It is seamless and automatic.

Our well pump is a Grunfos soft-start 120-volt model which runs off our house PV system. The distance from our house to the well made DC unattractive. Our pressure pump is 12 v. and runs directly from our battery bank.

Both the Grunfos and the Dankoff pumps we have are pricey, compared with some of the RV-type and other pumps. You can save a bunch of money with the cheaper ones, if you are not going to be running them very much. We live here full-time and I decided on beefier pumps. The Grunfos has only been in operation for about four years, zero trouble. The Dankoff has been in use for maybe 25 years. I replaced the brushes last year, just because I had them. The old ones still looked pretty decent, though of course showed wear.

Our area experiences months of cold winter weather. The ground is mostly rock. So I could not bury my line from the well to the cistern more than a few inches. I put a set of valves down at the well and I open them after filling the cistern and completely drain the line.

But do the well first.

Off Grid Water System

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