Adding pressure tank to irrigation well

Reply

  #1  
Old 03-05-16, 07:19 PM
B
Member
Thread Starter
Join Date: Mar 2016
Posts: 2
Received 0 Votes on 0 Posts
Adding pressure tank to irrigation well

Iím hoping someone can help me here or at least point me in the right direction. I just moved into a house with a shallow well for irrigation. The sprinkler system is in disrepair... The controller is missing entirely and several of the sprinkler heads have broken off, but the pump and pump relay are still there. This afternoon I wanted to see if it might be possible to revive this system, so I opened a spicket that had been installed on the output of the pump and manually operated the pump control relay. The pump ran, but didnít move any water. I have no idea how long it has been since the last time the pump ran, so I tried to prime it and start it again. This time water started gushing out of the open spicket, so it appears that the well is not dry and the pump is functional, so this makes me happy. Right now there is no pressure tank on the system. Just the pump and a pump control relay.

Now, I have two things I would like to do with this well water. First, I want to try to revive the sprinkler system, so I will need to get a new controller and install that as well as fix the broken heads. But second, Iím in the process of installing a 220 gallon saltwater reef aquarium. All the water for the aquarium needs to go through an RO/DI filter. It occured to me that I might be better off using this well water for the filter for the fish tank. Iím thinking there are two benefits. First, the aquarium uses a decent amount of water to top off the tank to replace water that evaporated and also to make new salt water for water changes. Using well water would be free (save the cost of power to run the pump), so that would be good. Secondly, the city water here is heavily chlorinated (I smell like Iíve been in a pool when I get out of the shower) and the chlorine is bad for the RO membrane. The well water would not be chlorinated, so I wonít have to worry about damaging the membrane.

From the research Iíve been doing, it looks like what I would need to do is get a pressure tank and a pressure switch. So I could provide pressure to the RODI filter without damaging the pump. So my questions, in no particular order are:

First, is this the right approach?

Second, what size pressure tank would I need for the sprinkler system and the RO/DI filter?

Third, do I need to install a check valve between the pressure tank and the pump?

Anything else I should know or need to consider?

Thanks in advance
 
  #2  
Old 03-05-16, 08:48 PM
C
Member
Join Date: May 2015
Location: USA
Posts: 3,138
Received 2 Votes on 2 Posts
Your approach sounds reasonable for the SWA use; I suggest you valve it so you can restore to tankless system when you want to run it for irrigation (although not strictly necessary).

If you know the flow rate of the R/O filter, you use that to size the pressure tank. Ideally, you want the pump to run for a short period and then shut off for a few minutes at least to cool. I suspect the R/O flow rate is very low, so only a small tank would be needed. Let's say the R/O inflow is 1 gal per minute (Probably way higher than it really is), then a tank with 5 gallon draw down would let the pump be off 5 minutes which is fine. You also don't want it to be so small that the pump only runs for a couple of seconds. If you can post details of your R/O we can help better with sizing.

You should install a check valve. That way if the check or foot valve in the well is leaky it won't draw down the pressure tank.

You may want to have the water tested for bacterial contamination if that would be a problem for your fish; I don't believe and R/O will correct that, although if the DI is a still, then probably no problem.
 
  #3  
Old 03-06-16, 05:51 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,753
Received 791 Votes on 728 Posts
A pressure tank is not required. Good to have but not required. Its job is to minimize the on/off cycling of the pump. The size of the tank will determine how much water you can use before the pump kicks on. When picking a tank look at the usable tidal volume or drawdown at the pressures you will have your switch set at. It's usually around 15% of the tanks capacity. So, if you get a 15 gallon pressure tank the usable tidal volume will be 1.5 to 2.5 gallons meaning when the tank is full and the pump cuts off you can use about 2 gallons of water before the pump kicks back on. Obviously bigger is better but you have to consider the size and expense of the tank against wear on the pump.

What is the depth of your well? Ground water often contains more dissolved minerals. Most municipalities get their water from surface sources like lakes and rivers which tend to have lower dissolved content. You may have to remove more minerals from the well water than you would from city water. Chlorine is easy to remove from the city water so I wouldn't let that influence your decision.

Where are you located? if it's in a area that gets below freezing you have to bury and run your water lines where they won't freeze. I assume your aquarium will be inside... where you already have piping for municipal water. You will have to run additional piping to bring your well water to the aquarium area. And don't forget that your RO system will be discharging a lot of waste water so you'll need to locate it somewhere it has easy access to a drain.
 
  #4  
Old 03-06-16, 11:04 AM
B
Member
Thread Starter
Join Date: Mar 2016
Posts: 2
Received 0 Votes on 0 Posts
Thanks for the suggestions. The RODI filter is a 75 gallon per day model, so even being generous allowing for wastewater it should use well under 1 gallon per minute, so I'm thinking a pretty small tank would be sufficient. I did take a look at the pump and it looks like it's a flotec fp5182-08, which apparently can move around 45GPM depending on the well depth and such, so while a 5 gallon (or smaller) tank is probably overkill for the RODI filter it sounds like I may get in a situation where the pump will only run for a few seconds to fill the tank.

I'm assuming that a small tank won't really be a problem for the irrigation system. Once the irrigation system calls for water it would drain a 5 gallon tank almost immediately and the pump would run the whole time it was calling for water, but that's not really an different than the way it's configured now. The pump runs the whole time the sprinklers are on.

Pilot, I live in central Florida and the pump and plumbing for it are already exposed, so freezing really isn't a concern here. As far as filter location, it's not installed yet, but right now my plan is to install it next to the water heater in the garage. That way if I decide to use city water I can just tap into the feed line for the water heater. The well pump is on the other side of the garage wall, so if I decide to go with the well I can put the tank inside the garage in the same place. Either way I'm planning to run the waste water through the garage wall into a garden or something.

The city water here is quite hard as it is, so I'm not sure the well water will be much worse, but it probably is worth testing before I get too far involved in this project.

Unfortunately I have no idea how deep the well is. It came with the house and I didn't get any documentation on it. I did see in the pump documentation that the max depth for this pump is 20 feet, and the water table in Florida is pretty high, so I'm guessing it's pretty shallow.
 
  #5  
Old 03-06-16, 06:05 PM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,753
Received 791 Votes on 728 Posts
Personally I'd use the well for irrigation but I don't think the RO system for your aquarium will use enough water to make it worthwhile hooking up to the well.

And, you must post some pictures of your reef tank once you get it set up.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: