Off Grid Water Pressure Tanks
We recently replaced the water pressure tank in our new to us (old) home. The old tank had bitten the dust.
Just in case you don't know this, pressure tanks are also called bladder tanks or household diaphragm tanks. And it probably needs to be replaced when your water pump is turning on more frequently than it used to. That's what ours was doing. The water pump would turn on after just 2 or 3 flushes of the toilet--now it only runs 2 or 3 times in the entire day!
Pressure Tank Theory For Beginners
Here's a little pressure tank theory for newbies. If you are familiar with pressure tanks, just skip to the next section.
If you live in a rural area, chances are that your water source is a well with an electric pump. While you'd like to have pressurized water 24/7, you don't want your pump to run 24/7. That's where the pressure tank enters. It keeps your water system pressurized when the water pump is not running. Once you've used enough water to drop the water pressure before a certain threshold, the water pump turns on again and pumps the pressure back up.
Pressure Tank Size
The major factor when choosing a pressure tank is the size. This can get a little confusing, so let me try to clarify this for you.
Typically, the total gallon capacity of the tank (if it was completely empty) is what is used for this. But be aware that some companies will also publish what they call the "Equivalent To ___" and then there will be some high number like 120 gallons or so. Don't be confused by that. You are looking for the total volume of the tank, not the figure that is equivalent to an old galvanized pressure tank.
Our old tank was 40-50 gallons (it was so old, I'm not sure about the exact number). The new tank we installed is an 86 gallon tank.
The other figure you'll see thrown around is the drawdown capacity. This is the actual amount of water your tank can hold at the given pressure range you operate in. For our 86 gallon tank, the actual drawdown capacity for our pressure range is around 30 gallons. This means that once the tank is fully pressurized, I should be able to use 30 gallons before the water pump turns on again.
Why did we install such a large tank when the trend these days is to use a tiny pressure tank? Here are a few reasons why I think large pressure tanks are a better idea for any rural homestead--especially if it's off the power grid...
Advantages of Large Pressure Tanks
- Easier on the water pump - The larger your pressure tank, the fewer times your pump has to turn on and off. Typically, starting and stopping a lot is hard on a water pump, so a larger tank should be easier on it. Bear in mind that it may be a little different if you are using one of the new variable speed pumps.
- Less power consumption - Every time a water pump starts, it requires a short surge of electricity to get it up and running. If it uses 1,200 watts when cruising, it could take 3,000 watts (as an example) to get it started. A larger pressure tank means there will be less starting and less surging. This means a little less power usage. And if you are off grid and using a small undersized inverter, large surges can be challenging if you have a bunch of other things on in your home.
- Emergency capacity during a power outage - This is especially important if you are connected to the power company. During a blackout, your water pump loses power too, so the only water accessible to you is what is left in the pressure tank. If your pressure tank is large, you have a better chance of making it through a short blackout without running out of water.
Bottom line? Whenever you install a new pressure tank, put in the largest one you can afford/fit in the allotted space.
Perhaps the best-regarded brand in the industry is Well-X-Trol. That would have been my first choice as I really appreciate quality and try to go with a quality option whenever possible. But I also have to balance quality with price and weigh the cost against the benefit. When I discovered that the full Well-X-Trol model was nearly 3 times the cost of the brand I was looking at, I decided to take a chance on Water Worker (which is the lower quality line made by Well-X-Trol).
As a backup plan, I made sure to install a union on either side of the tee where our pressure tank connects into the water system. That way, if the Water Worker model doesn't last well, it will at least be easy to change out :-).
Excellent video; concise and informational. I find it interesting that your water pressure tank is indoors; I live in Florida and these tanks are always outside at the pump site. Of course, we rarely have freezing weather, and I just never really thought about it.
You know, I forgot to mention about our pressure tank being inside :-). I have lived in the South and have seen many pressure tanks outside as well (or often it might be in an unheated garage). But up here in cold country, we can't get away with that--hence inside it goes. The other option I've seen up here is to build an insulated pump house around the well head and pressure tank, but the downside with that approach is that you have to come up with some way to heat it during the coldest months. Insulation only keeps things from freezing up for short cold spells. Consistent cold requires heat.
I stumbled on this while planning an entirely outdoor setup - a campground that school kids come to through the year, and we're currently carting dishes across the road to our on-grid building to wash and back, which is not the most efficient use of time or resources!
If I had the pressure tank and well head in an insulated enclosure, and ran the system dry before the first hard frost, do you think it would be alright when I started it up again in the spring? I don't think we'll be using it much after the end of October, and I hate to build a fully heated enclosure when I don't have any other consistent heating needs on that part of the property.
Nick, I'm building my off-grid house currently, and your timing of this information could not be better! My question is in my application I plan on having the grunfos sq flex well pump pump into an 1100 gal. Holding tank. The system is elevated above where it comes into the house so if the sun isn't shining I can still gravity feed into the house. Based on this information you've presented, it seems like I need to use the large tank to then keep the pressure tank full. So my system would be the following: water is pumped into my large holding tank. It then feeds into the pressure tank which then feeds into the house. Do I still need a DC pump to push the water into the house , or is the pressure tank all I need?
If a person has enough "head", meaning the holding tank or water source is high enough to create the necessary pressure, there is no need for a pressure tank. Just measure the pressure of the water coming from you holding tank to determine that. Household pressure should usually be between 45-65 PSI. However, I have lived in a house with much less under gravity fed.
Great point, Michael! I agree with you that gravity feed systems are definitely the best (if the layout of your land supports that option). Only trouble is that you must have a hill nearby (which we don't). But if you do, it's pretty awesome, isn't it?! Then you can use a super efficient slow pump to push the water up to the tank on the hill and gravity takes care of the rest. Really, the ultimate is if you have a natural spring up-hill from your home. Then it can collect in a cistern and gravity flow the entire way without a single watt of electricity. Very nice!
Our water pressure is 25-45 PSI which we have found to work well, but if we wanted to, we could bump it up higher. Just figured we don't really need it any higher, so why put extra strain on the pump and use more power if not needed? The main appliance I'm aware of that has a substantial minimum pressure is an on-demand water heater, and as far as I'm aware the minimum is 20 PSI. But from experience we've found that ours works better with a minimum of 25 PSI.
Anyhow, thanks for the great input, Michael! Take care
Hi Mike, Sounds like a nice water system you are setting up! As long as your 1100 gal. tank is elevated high enough above your house (or point of use), then there is no need for an additional pump or pressure tank.
How high the tank needs to be depends on how much pressure you are willing to deal with. There are people out there who live with less than 10 PSI of pressure, but it's not much and some appliances like an on-demand water heater may not function properly with less than 20-25 PSI. So unless you are okay with low pressure, I would recommend that you not settle for less than 20-25 PSI, and 30-40 PSI would be even better and would deliver pressure more like what you are probably used to.
What does it take to get that kind of pressure? For every 1 vertical foot that your water cistern is above your point of use, you'll get roughly .43 PSI of pressure. So 10 feet of vertical rise should yield around 4.3 PSI. That means you are looking at around 58 vertical feet of rise to get 25 PSI.
If you are unable to get the cistern high enough to have enough water pressure, then you certainly could add a DC booster pump or pressure pump at the house to boost the pressure up to regular household pressure. In that case, you would want a pressure tank installed. But in that one instance, having a large pressure tank is not quite as critical as it is in most other instances. Gravity is likely doing much of the work for you and DC pressure pumps generally use very little power and surge little no none. So while I wouldn't get a tiny pressure tank, you probably don't need a very large one like ours. And the beauty of this system is that even if your DC pump were to die, you should still have flowing water in your home thanks to gravity. The main difference would be that the pressure is diminished when the pump is not working. Depending on the pump, you might have to plumb in a bypass to circumvent it while repairing it. But honestly, if you go with a high quality pump (like a Dankoff), you should have many years of good service.
Hope that helps,
Good stuff, Nick. It would be hard for me to remember in perpetuity. While not quite as easy to use as your coefficient, I do find it easy to remember that 27" of water column is a psi. 2'3". So, I have to convert feet to inches, divide by 27 for psi, then use divide by 12 to get back to feet. More steps, but 27" is all the NEW stuff I needed to learn... for just lil ole me. If you ran a looong skinny (cheap) pipe you could just call it 2 feet, because friction will rob some flow, reducing [effective] psi a bit. You will MEASURE full psi, at rest, but some is lost when using flow. It's all common sense if you just ponder it a bit. Einstein said, Imagination is more important than intelligence. I might argue that they are brothers, but I get his meaning. He had to imagine his workbench and parts. But every worker has to do this in the beginning.
Great article Nick, you really nailed it. I've been wondering about this issue for a long time in relation to my home well set up. I'll be on the look out for the biggest tank I can afford now, to give us backup water for when the grid goes down, which happens often enough to be a nuisance. Thanks again for your great advise as always. Garry
Thanks Gary, Glad it was helpful.
Years ago living in a small community we actually had a 1500 gallon tank that was used as our pressure tank. Sure was nice after Hurricane Katrina. Start the generator, flip on the breaker to start the well, fill the tank with 1,000 gallons or so and then turn everything off. Galvanized tank with an air valve works well.
That's really interesting. Anytime I can have a larger supply of water on hand, I'm all in! And 1,000 gal. of water is really nice to have on hand. Can be very handy if you have to deal with a fire also.
Thanks for sharing,
We bought our homestead in 1991. We are on the grid. Our system is much like Mike's. We pump into a 1500 gallon elevated tank which connects to the pressure tank and then on to the house. Should we have an extended power outage, we can gravity feed water to our home and out to the water troughs in the pastures. The pressure tank is 20 gallons and sits about 300 feet from our home.
Thanks for sharing! Sounds like a great system. I'm curious about why you have a pressure tank on your system since it is gravity flow. Maybe I'm not understanding the whole setup. Perhaps you have a booster pump to boost your pressure (due to inadequate gravity pressure)?
Anyhow, I REALLY like having a large supply of water on hand like you do. We actually have a spare 1,500 gal. cistern filled up nearby for fire season. Cheap insurance and peace of mind :-).
We also have a 1500 gallon rain water tank which is gravity fed to water our large garden. I, highly, recommend harvesting rain water.
Yes, if our water source was not reliable then rain water might be something we would look into. The challenge in our climate is that probably 90+% of our precipitation falls in the late fall/winter/spring, and then we have the summer months with almost nothing. So it would take an enormous holding tank to supply us for months during the very time when we use the most water (irrigating, etc). But I'm sure that in some situations and other climates, rain water could be a great supplement to one's main water source. I'd just couldn't bring myself to rely entirely on rain water, as I've been through too many droughts. But I like you idea of using it as a supplement for irrigation (as long as you actually get some rain in the summer).
Thanks again for sharing!
Thanks for the advise on pressure tanks and selecting sizing.
You are very welcome, Barry. So glad you found it helpful.
Nick, as an old country boy my grand showed me a secondary trick for water storage and I still use it on our rural property. We have our main water supply and we'll system. However I have an additional 1000 gallon stand by tank. We have the main system which holds 150 gallons which pumps in to a 1000 gallon under ground tank. I have it hooked up to a toilet tank valve set at a level. When the big tank drops to the level the main system comes on. To have the pressure I use a shallow well pump with a small gallon pressure tank. This works great for us.
We have lost power here in Oregon for seven days and we still had water. I used my truck inveter to power the little pump.
I also ported a 1"1/2 Forestry hose bib up to the tank for fire fighting purposes which I can draw off of if we ever need it.
Hi Brian, the toilet tank valve is an interesting idea. I used one of the float switches available at most pump shops. It gives a much greater drop in level before turning the pump on. I used a 24 volt relay to turn on my pump which is a couple hundred feet away. I can see where your idea would be a great help for a far remote pump.
Good point, Dave. I too would prefer a typical float switch. I've also seen an interesting idea which is an electronic switch which doesn't move and detects the water level. While I typically like manual rather than electronic options for things like this, the selling point is that you don't have to worry about icing making your float switch stick. But as long as your tank is buried where it never ices on the top, then that probably isn't an issue.
Thanks so much Brian for sharing that! I like much of it, especially having your main water system keep the 1,000 gal. tank topped off. It makes you feel really good to have a bunch of extra water on hand whenever you need it, doesn't it?!
And like you mentioned, it's important to have that extra capacity during fire season. We have a spare 1,500 gallon tank in our shop for fire season. Cheap insurance!
Thanks again, Brain. Take care,
Thanks for putting this information together Nick. We just finished our off grid water system and like you, opted for the larger pressure tank to reduce cycling of the pressure tank and booster pump. Water systems can be just as variable as solar systems. It all depends on the variables of the site and user needs.
For our system, we used an efficient Dankoff 120v booster pump to charge up the booster tank which is about 80 gallons in size or so. Dankoff has 12, 24 and 48 volt DC versions of this booster pump too.
We did not have enough elevation for a pure gravity system but there is enough elevation to give us about 12 psi at the house so even if the booster pump and pressure tank fails, we can still wash our hands or flush a toilet until the system is repaired.
Thanks for putting these videos and blogs together. I've learned much from you and your parents over the years.
That's awesome, Joe! Sounds like a fantastic water system. So nice that you have gravity working with you in case you were to lose power! You could actually do a lot with 12 PSI, but I would have done the same as you did--install a Dankoff booster pump to bump the pressure up. And those things use such a small amount of power! Very nice.
Thanks again for sharing. Take care,
Hi Nick, I see you used the plastic unions. May I suggest that you install a stainless hose clamp on each end of the union (the part that the nipples thread into). I have had several split and they can leak a lot of water. Haven't had any split since I started putting the hose clamps on...
Also like Brian, I pump into a large (2500) gallon underground tank up on the hill behind my house. I get about a weeks supply of water at around 23 lbs/sq-in. Also a lot less pump starting and stopping as it drops over 500 gallons before restarting.
Hi Dave, Thanks for that tip. Sounds like a really good idea that I will probably implement.
Yes, I was a little nervous about using PVC unions since I'm used to using metal ones. But since the existing plumbing was PVC, I decided to stick with plastic since I've found that making a transition from plastic to metal doesn't always go so well either. So I went with Schedule 80 unions (rather than the typical schedule 40) since they are stronger, and I also put some silicone lubricant on the o-rings to hopefully keep them supple and give a good seal. But I really like your hose clamp idea--makes a lot of sense.
Thanks again for the great idea! Take care,
QUESTION ABOUT AUTOMATED WATER TIMERS ON A FROST FREE HYDRANT:
I have frost free hydrants with hoses around my garden to water vegetables as well as the orchard. The research that I've done is inconclusive as there is so much contradiction and differing advice. I really don't know how to proceed. I'd like to set timers to water the veggie raised beds, however I'm worried about leaving the hydrants open for hours.
Do you have some easy steps to share as well as suggestions for the devices required?
I will greatly appreciate some guidance here. THANK YOU SO MUCH for all the valuable information you have in "Sustainable Preparedness".
There should be no issue at all with leaving a frost free hydrant open for extended periods of time, as long as it is a time of year where there is no danger of it freezing. The 2 things to look out for with frost free hydrants are:
1 - Lots of opening and closing of the valve. Every time you close the valve (turn the hydrant off), it opens a weep hole at the bottom of the hydrant (underground) and lets all the water above weep down into the ground. If you are doing that frequently, you could saturate the ground under the hydrant and it might not be able to properly drain down. This may not be a huge problem in the summer, but could result in a frozen hydrant in the winter.
2 - Leaving a hose connected when you turn the hydrant off. Doing this makes it so that the hydrant either cannot drain down, or else it tries to drain the contents of the entire hose through it's weep hole and into the ground. Neither of those are a good situation, especially in the winter.
Hope that helps!
Enjoyed your pressure tank video. Question -- We are building off grid home and for now (until our spring is fully developed) catch rain water which is dumped into a 1500 gallon tank. Now regarding getting the water pressurized and back to our house. 1) what kind of 120 volt pump would you recommend in either a submersible version or external pump version? Any specific brands and/or models?
I have a stream running through my property that has good water flow year round. My house sits up hill from the creek, but there is no where I can put a gravity tank above my home. I was wondering if I could use a pressure tank to get the water pressure I need for my house water?
Is a pressure tank needed in a gravity fed off grid system?