(Another) Pressure tank drawdown question, new tank install

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FingerLakes

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I just installed a new WaterWorker HT86b 86gal diaphragm pressure tank. All new hardware, tank T, valves, gauge etc.
Measuring by running the garden hose into 5 gal buckets, I am getting approximately 18 gal drawdown.
The spec sheet for the tank says drawdown is 26 gal at 30/50 and 23 gal at 40/60.

I am using a 30/50 switch adjusted a little to 33/53 cut in/out.
The air pressure in the tank is set to 31psi, or pretty close. I used two different tire gauges and got the same reading so I think it is fairly accurate.
My submersible pump is 10gpm and it cycles for 2min 30 sec to fill the tank.

I dont expect the drawdown to be exactly 26 gal, but is 18 way off? Should I be troubleshooting to chase down a few more gal of drawdown and where would I start to do that? Or should I just be happy with the tank as is? Everything with the tank and water pressure in the house is functioning good.
I am leaning to leaving well (no pun entended) enough alone since this is a huge improvement over the 4-5 gal drawdown I got from my last tank.

Thought or recommendations?

Thanks for your help.
 

Valveman

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My calculator shows 25.41 gallons with a 33/53 switch.

You say "approximately 18 gallons" and the company is probably exaggerating their estimate. 2 minutes 30 seconds is a good run time and means a 10 GPM pump is putting 25 gallons in the tank. With a 5 GPM demand like a sprinkler running for hours or all day, that would be a cycle every 10 minutes, which is still 144 cycles per day. That is much better than the 300+ cycles you would get with a 20 gallon size tank, but still not good for the pump.

The tank size and draw down amount becomes a moot point when a Cycle Stop Valve is added. The same 5 GPM demand that would cause 144 cycles per day with an 86 gallon tank or 300+ cycles a day with a 20 gallon tank would only cause ONE cycle per day with a CSV, no matter what size tank you have.
 

FingerLakes

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Thank you for your reply Valveman.

I am just trying to determine if 18 gal drawdown is "normal" for this tank which the mfg says could be as much as 26 gal drawdown. I will contact the mfg directly and ask them next. I said "approximately 18 gallons" because i did not measure the amount precisely but used 4 buckets and eyeballed the measurement a bit. If I should be getting more drawdown, I'd like to know how to go about it.
I am happy with the performance at present but just want to get another opinion. Does anyone have any thoughts on this part?

I understand the 2.5 minute pump cycle is good and it is probably pumping 20-21 gal to the tank. I did not mention before but this is a drainback system so there is a delay for the water to reach the tank while it fills the pipe run and expels air through a valve just before the tank. My previous system was the old fashioned air over water tank which was functional. I upgraded the system solely to gain a higher drawdown and save wear on my 2yr old pump.

I have read about the CSV valves and they seem useful for many applications. I did not think I needed one for mine. Mine is a 2 person household. I dont have a sprinkler system. Where a CSV valve would benefit me most is when watering the garden i guess, or filling the hot tub, but that is at most 3 times a year for the hot tub. Would a CSV valve be functional if I placed it in line before my garden hose spigot? Or must it be installed before the pressure tank?

Thanks.
 

Valveman

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Pump systems will work fine without a CSV. They will just work much better and last much longer when using a CSV. Yes, the CSV must go before the pressure tank/switch, and before any hydrants or tees in the main line. The CSV will really help when watering the garden, filling a pool, or other things like that. But the CSV will also give you strong constant pressure in the showers and make appliances fill faster and work better. The soft start/stop when using a CSV helps no matter how the water is being used. The drain back system will require a little larger tank than usual with a CSV, but will make a few gallons of draw down a moot point.
 
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