Well Tank : Small tank w/ CSV or medium tank w/ CSV or standard pressure tank

[anothermineral]

First off... Happy New Year!

Here's my dilemma....

I currently have a Well x Trol 203 (32 Gal) with a 30/50 switch servicing my single family house (just two adults living in the house). The tank is ~18 years old and very rusty (partially due to me, more on that in a bit). I've had no issues with this setup thus far. Unfortunately, I don't have any info on the type of well pump or the depth of the well.

I breed clownfish as a hobby/second job. I have a "fish room" which is collocated where I have my pressure tank and in that room, there is ~750 gallons of salt water in multiple tanks. In my opinion, this has greatly accelerated the rusting of the well tank.

One of the ongoing needs for the fish tanks is to be able to replenish fresh water due to evaporation. I have a 75 GPD RO/DI system with it's own booster pump that handles this nicely. As many of you may know, there is a substantial amount of waste water created when producing RO/DI water. I estimate I waste 3-4 gallons for every gallon I create.

So now to my question(s):

1. I'm replacing the current well tank regardless. I've read a lot about smaller tanks with a CSV vs. my current configuration of just having the WellxTrol 203. I'm not overly concerned about constant pressure, as this has never been a problem, however, since I'm constantly creating RO/DI, (sometimes 50+ gallons per day, which could equate to as much as 200 gallons pulled up through my well given the waste equation), would I benefit (less stress on the pump, less stress on the overall system, etc...) with a setup with a CSV vs. the current system I have?
2. If I were to go with a CSV setup, would there be any benefit to using a larger tank like the wx-202 (20 gallons) vs. the wx-102 (4.4 gallons) that's typically recommended? For instance, the pump would not cycle during a toilet flush and other similar low volume needs, but would run when I called for water for either a shower or to produce RO/DI.
3. Given my corrosion prone environment, is there a poly/fiberglass tank out there with the same performance/quality as the WellxTrol tanks? I've read up on the Flexcon Flex-Lite tanks and they appear comparable in their butyl diaphragm lining. I've also seen 4.4 gallon stainless steel tanks offered as part of the CSV setups. I'm a big fan of stainless given my current environment.

Final thoughts... Money is not an issue here, I'm more concerned about longevity/reliability/piece of mind. I realize I'm taxing a "home system" by running the fish room, and want to ensure that whatever course I take, it has been correctly engineered for the lowest failure possibility of the entire system as a whole. That said, it appears that any of the above scenarios will run between $450 - $600 for the parts.

Appreciate comments to the above or to any other options I may have missed.

Thanks,

Tony

 

[Reach4]

In your RO system, is that load pretty much spread out or is the water draw more in spurts? If fairly continuous drawing about 8.3 gallons each hour, the CSV would not seem to be a good fit.

How long does your current tank take to fill?

This sounds like a good match for the Flexcon FL17 would be bigger unit than you have now. Big is good for function. FL12 would be just a little bigger than your current tank.

I am not a pro.

 

[Sponsor]

 

[anothermineral]

In your RO system, is that load pretty much spread out or is the water draw more in spurts? If fairly continuous drawing about 8.3 gallons each hour, the CSV would not seem to be a good fit.

How long does your current tank take to fill?

This sounds like a good match for the Flexcon FL17 would be bigger unit than you have now. Big is good for function. FL12 would be just a little bigger than your current tank.

I am not a pro.

Thanks for the quick reply.

The RO/DI demand varies, some days I need to make 50+ gallons, some days I make less than 10.

Current tank (wx-203) fills in ~30 seconds with the water running and in ~15 seconds when not running.

 

[Reach4]

Thanks for the quick reply.

The RO/DI demand varies, some days I need to make 50+ gallons, some days I make less than 10.

Current tank (wx-203) fills in ~30 seconds with the water running and in ~15 seconds when not running.

If your current tank takes 15 seconds to fill with no water running. and if the current tank is working OK, you should have a pressure tank with a drawdown that is about 4 times your current tank. Your pump should run at least a minute each time, even if the water use stops right when the pump cuts on.

Have you checked the precharge on your current tank? It should be 2 PSI below the cut-on pressure for a submersible pump. I would check/set that precharge now-- one reason would be to get a better assessment of how large of a pressure tank you really should have when you do replace your tank. Precharge is checked/set with zero water pressure. Now is the current tank giving you the drawdown that it should? If you had info on your pump (HP and GPM rating) plus how deep the water level in your well is, we could figure out about how many GPM is delivering into your 40-60 PSI (or whatever it is) system.

 

[LLigetfa]

I currently have a Well x Trol 203 (32 Gal) with a 30/50 switch

There is less than 10 gallons of drawdown on that tank.

 

[Reach4]

A higher pressure switch setting will make the RO work better.

 

[Valveman]

A WX203 only holds about 8 gallons of water. If you are making 50 gallons of RO with a 4 to 1 waste factor, that is 250 gallons per day. That means the 8 gallons in the tank will drain out over 30 times per day, making the pump cycle at least 30 times per day. Then you can probably add another 60 cycles per day for the average 600 gallons used by two people in a house everyday. So if the bladder in the WX230 is still good this adds up to about 100 cycles per day. And you would need a tank 4 times that size to get the one-minute of run time for the pump like Reach said.

You can use as large a tank as you want with a CSV. However, as long as you are using more than 1 GPM the CSV makes water go right past the tank, straight to the faucet(s). So if the RO is drawing more than 1 GPM, the pump will just stay on until the RO shuts off. Showers use more than 1 GPM, so the pump just stays on as long as the shower is running.

Using a CSV to keep the pump running when water is being used for extended periods of time will probably cut the cycling in half, even with the 4.5 gallon size tank. Using the CSV with a larger tank might cut the cycling a little more, depending on how many times a day a toilet is flushed by itself and only one time. When a toilet is flushed repeatedly multiple times, the CSV just keeps the pump running until you stop flushing the toilet. When a toilet is flushed while the RO is making water or while a sink, shower, or any other water is running, the pump does not see an extra cycle, even with the small tank.

There are applications where a large tank with the CSV is helpful. But in your case, when you see how the CSV works, you will realize a larger tank is just a waste of space and money. And yes you can use Stainless Steel or a Fiberglass tank. But the standard little tank that comes with the CSV kit will last a long time even in a salt environment, and then it is only about 70 bucks to replace when needed.

With run times so short I am surprised your pump has lasted this long. With any size tank you choose, the CSV will extend the life of the pump by eliminating short run times and excessive cycling.

 

[anothermineral]

A WX203 only holds about 8 gallons of water. If you are making 50 gallons of RO with a 4 to 1 waste factor, that is 250 gallons per day. That means the 8 gallons in the tank will drain out over 30 times per day, making the pump cycle at least 30 times per day. Then you can probably add another 60 cycles per day for the average 600 gallons used by two people in a house everyday. So if the bladder in the WX230 is still good this adds up to about 100 cycles per day. And you would need a tank 4 times that size to get the one-minute of run time for the pump like Reach said.

You can use as large a tank as you want with a CSV. However, as long as you are using more than 1 GPM the CSV makes water go right past the tank, straight to the faucet(s). So if the RO is drawing more than 1 GPM, the pump will just stay on until the RO shuts off. Showers use more than 1 GPM, so the pump just stays on as long as the shower is running.

Using a CSV to keep the pump running when water is being used for extended periods of time will probably cut the cycling in half, even with the 4.5 gallon size tank. Using the CSV with a larger tank might cut the cycling a little more, depending on how many times a day a toilet is flushed by itself and only one time. When a toilet is flushed repeatedly multiple times, the CSV just keeps the pump running until you stop flushing the toilet. When a toilet is flushed while the RO is making water or while a sink, shower, or any other water is running, the pump does not see an extra cycle, even with the small tank.

There are applications where a large tank with the CSV is helpful. But in your case, when you see how the CSV works, you will realize a larger tank is just a waste of space and money. And yes you can use Stainless Steel or a Fiberglass tank. But the standard little tank that comes with the CSV kit will last a long time even in a salt environment, and then it is only about 70 bucks to replace when needed.

With run times so short I am surprised your pump has lasted this long. With any size tank you choose, the CSV will extend the life of the pump by eliminating short run times and excessive cycling.

Valveman, Thanks for the reply. What's the theory about the should take time for the tank to fill to be about a minute? Wouldn't this also be a factor of the type of well pump you had and not necessarily the proper tank size for your water needs?

Also, I was thinking that maybe the smart thing to do would be to separate the house water system from the fish room system. I could put in a large poly tank (250-300 gallons) and use that to draw water for the RO/DI. This way the well pump would only cycle once or twice a week for the purposes of filling that tank and then I could use a smaller pump to feed the RO/DI. This could allow me to use the CSV system with a smaller tank for my house needs and then just fill the reservoir tank as needed. Thoughts?

 

[LLigetfa]

I doubt the RO system will draw more than 1 GPM to keep the pump running with a CSV so a larger tank should be used.

As for sizing for a minimum of runtime, it is all about dissipating heat. There is an inrush of current on start that takes time to dissipate and dissipate it does while the pump is running. The rule of thumb minimum is one minute.

 

[Valveman]

What's the theory about the should take time for the tank to fill to be about a minute? Wouldn't this also be a factor of the type of well pump you had and not necessarily the proper tank size for your water needs?

In the past, rule of thumb has always been to size the pressure tank according to the size of pump. You want the pressure tank to accept as much water, as the pump will produce in one minute. Filling the tank in one minute is the minimum acceptable, two minutes is better, and no cycling on/off at all is best. When running at Full Service Factor Load, submersible pumps need to run at least one minute to dissipate the heat from starting. Then they need to stay off for at least one minute to cool down before restarting.

None of that applies when using a CSV. For one thing the CSV makes the pump draw low amps, not Full Service Factor Amperage. Starting and running at reduced amperage means the pump no longer needs to run for a minimum of one minute. Then because when using a CSV the pump never shuts off as long as water is being used, you no longer need to worry about 1 minute of off time for the pump. The pump will just stay off until the next time you use water.

The CSV causes extended pump run times when you are using water, which is good for the pump/motor. The CSV runs the pump at reduced amperage, which is good for the pump/motor. The CSV doesn’t let the pump shut off until you are finished using water, so pump/motor off times are extended, which is good for the pump/motor.

Also, I was thinking that maybe the smart thing to do would be to separate the house water system from the fish room system. I could put in a large poly tank (250-300 gallons) and use that to draw water for the RO/DI. This way the well pump would only cycle once or twice a week for the purposes of filling that tank and then I could use a smaller pump to feed the RO/DI. This could allow me to use the CSV system with a smaller tank for my house needs and then just fill the reservoir tank as needed. Thoughts?

I would just install the CSV and small tank first. I think the RO will have a steady draw that will not cause the pump to cycle. IF the RO or anything draws water in small intermittent spurts, which I don’t think it will, you can always add a little larger pressure tank to take care of that. I think when you see how the CSV works you will realize the small pressure tank is all you need.

 

[Valveman]

I doubt the RO system will draw more than 1 GPM to keep the pump running with a CSV so a larger tank should be used.

As for sizing for a minimum of runtime, it is all about dissipating heat. There is an inrush of current on start that takes time to dissipate and dissipate it does while the pump is running. The rule of thumb minimum is one minute.

When using more than 1 GPM the CSV makes the pump run continuously. Even with a ½ gallon being drawn from the system, the CSV with the 4.5 gallon tank will cause the pump to run for 1.18 minutes and be off for 2.36 minutes. This more than covers the minimum run and off times required by motor manufactures, and is much better than what you have now.

On top of meeting the minimum run and off times using only a 4.5 gallon size tank, the CSV also makes the pump run at reduced amperage. This means the pump/motor runs cooler and doesn’t even require those minimum run and off times. The only time I would install the CSV with a larger tank is if you are going to be using less than 1 GPM for more than a couple hours per day.

 

[anothermineral]

Thanks to all for your comments/recommendations.

 

[anothermineral]

I think I've figured out how I'm going to proceed, but would appreciate it if someone could check my logic/math to see if I'm not factoring in something important or just missing something altogether. Again, thanks for all the info above. It has basically led me to the following conclusions.

Assumptions regarding making RO/DI:

• Worst case scenario would be I'm making 75 GPD (this is the max my unit can produce per day).
• Assume 4 gallons of waste water for every gallon of RO/DI created (375 gallons used per day)
• So 375G per day assuming continual use would be ~.26 GPM

Since I'm below the 1 GPM threshold for the CSV, I think this means a CSV system with a small 4.5 gallon tank would need to come on ~every 4 minutes to produce the 75 gallons of RO/DI per day (that would be 360 cycles per day... Yikes!).

Conclusion:

• Install a Flexcon FL7 (22 gallon tank) with a CSV valve.
• The drawdown at 30/50 is 7.5 gallons, which I believe means that the well pump would only cycle ~every 30 minutes to produce the RO/DI (7.5G / .26GPM = ~29 minutes)
• That would have the well pump cycling only 48 times per day

The difference in cost of going with the larger tank CSV system is only $30 more.

The other option I was considering was to just install a FL17 (50 gallon tank) w/o a CSV. This would cost ~$100 more, but would reduce the pump cycling to ~23 times per day while making the RO/DI.

Thanks again for all your help!

 

[Reach4]

The other option I was considering was to just install a FL17 (50 gallon tank) w/o a CSV. This would cost ~$100 more, but would reduce the pump cycling to ~23 times per day while making the RO/DI.

You might even try your analysis on the FL30. Throw in 10 toilet flushes and 2 showers.

 

[Valveman]

If the RO system runs 24 hours per day at .26 GPM, the larger FL7 would be better with the CSV. If it is really a continuous draw of .26 GPM, adding a 375 gallon storage tank would eliminate many more pump cycles. In this way your well pump would only cycle once per day to fill the 375 gallon storage tank. Then you could use the CSV with the 4.5 gallon tank for everything else.

 

[anothermineral]

If the RO system runs 24 hours per day at .26 GPM, the larger FL7 would be better with the CSV. If it is really a continuous draw of .26 GPM, adding a 375 gallon storage tank would eliminate many more pump cycles. In this way your well pump would only cycle once per day to fill the 375 gallon storage tank. Then you could use the CSV with the 4.5 gallon tank for everything else.

Valveman, Yes, I was thinking that as well, however, now I would need an ~$400 poly tank and the space to keep it. For me it's really not a big deal as I currently have 16 fish tanks collocated in the same room, but if I'm going to put another tank in that room, I'd prefer to fill it with fish.

The continuous draw of .26 GPM is really a worst case scenario for flow. It assumes the only call for water in the house is the RO/DI and it's running 24 hours / day.