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 :-).