New house/well CSV setup

[FarmPondFalcon]

We're about to build a new house with "country plumbing" (well & septic systems) ... two adults, occasional addition of children and grand children. We'll probably install lawn irrigation for (say) a quarter or half acre of landscaped grounds. Our well has been drilled, 150 feet deep and 25 gpm (hooray).

I've been reading about alternatives; it seems the top two choices are (1) "Conventional" -- sizable pressure tank and constant speed pump, and (2) CSV system -- mini tank and the same pump.

My dilemma: it seems to me that the conventional system would be fine and easy on the pump and plumbing for the intermittent, small volume usage of our everyday living, but that the CSV system would be the star performer for the irrigation workload (but in our New England woodland, I imagine that lawn watering will be a not-very-often demand, and only a fairly short season).

How about seeking the best of both? Would it be feasible to have a sort of hybrid installation, such that the constant pressure CSV system operates when there's a relatively long call for water, but no need for the pump when it's just a small demand for ordinary household activity (other than to refill the pressure tank, of course, when it's been drawn down)?

[valveman]

With an old style pressure tank system, you need a tank that will have at least 1 gallon of draw down for each gallon per minute the pump will produce. Ie; a 10 GPM pump needs a tank with 10 gallons of drawdown, which is about a 40 gallon size tank. This should let you wash toothbrushes, fill the ice maker, or flush about 5 or 6 times before the pump is started. Adding a CSV to this system will still let the same thing happen. However, any use more than 10 gallons and the CSV will match the demand, which keeps the pump running continuously until the faucet is closed. You don’t need to bypass the CSV for this to work. Just set the pressure switch and CSV so it takes the right amount of time to refill the pressure tank. Ie; 40/60 switch, CSV set at 55 PSI.

With the CSV and small tank system, you only need a 4.4 gallon tank, that has 1 gallon of draw down. 1 gallon will keep the pump from having to start for small amounts of water like, washing a toothbrush or filling the ice maker. Any demands more than 1 gallon, and the CSV will match the demand, which keeps the pump running until the faucet is closed.

Actually the CSV and big tank are the best of both worlds for the pump. The big tank supplies water for smaller uses, while the CSV prevents cycling for long term uses of water. This delivers the minium cycles per day possible for any system, and extends the pump life considerably. The only draw back is that you have to wait for all the water in the tank to be used before you see constant pressure. Usually a person will be about half way through with their shower before the tank is empty and they experience constant pressure. Once you have experienced constant pressure, you will learn to hate waiting for it. Constant pressure is so much stronger than tank pressure for a shower, that you will quickly learn to like it. Many people have told me that with constant pressure, they no longer need soap in the shower, as the pressure will simply blast the dirt off of them.

The CSV and small tank are usually best for the home owner. The 4.4 gallon tank is less expensive and takes up less space. The pump will cycle a few extra times per day compared to the large tank system. However, you don’t have to wait for the constant pressure. When taking a shower, the pump will be running and delivering constant pressure, before you get the water temperature adjusted. With a larger tank, you would be continually adjusting the temperature of the water as the pressure dropped from 60 to 40 for the first half of the shower. With a smaller tank, the CSV will maintain 50 PSI constant and you will not need to adjust the temperature for as long as you are in the shower.

The CSV takes out so many cycles during long term uses of water, that you can afford a few extra cycles per day for short term uses of water. The CSV will work with any size tank, and the decision is ultimately up to your own preference.

[FarmPondFalcon]

Thanks for the information, both Snake and Valveman!

I see another issue that seems to me to argue for the larger pressure tank. Living in the country as we do, we're subject to power outages from time to time. We're what're called "elderly", and power outages threaten us about loss of heat and water and cooking and such, so our new house will certainly have an auxiliary power supply.

Wouldn't a small pressure tank, with more frequent starts of the water pump, come around to needing a substantially larger capacity in the generator?

We'll need to scale the generator to keep the heating system active, keep the fridge and freezer cold, and keep us in enough water for toilets and hygiene -- oh, and power up my computer! -- but I thought the competing demands other than water could be shut off long enough to refill a water tank once or twice a day, then returned to the heat and appliances duty.

Any thoughts?

[Bob999]

Motors--as in water pumps--typically take 2 to 3 times the starting current that they require to run. So in sizing a generator the sizing factor will be the starting current for your water pump plus any other motor starting currents and plus all other loads that are wired to the generator circuit. Obviously if you will manually control what loads are active at any time you can reduce the size of generator necessary but manually controlling loads can get to be a real pain if you are on generator power for any length of time.

[valveman]

With a generator I would use an 86 gallon pressure tank. Put in only 25 PSI air, set the pressure switch to 40/60, and the CSV at 58 PSI. When you are running on the generator, manually run the pump to 58 PSI and shut it off. Then you will have about 40 gallons stored in that tank you can use as the pressure drops from 58 to 25 PSI. You can use a lot smaller generator if you run the pump by itself, fill up the tank, shut off the pump, then use the generator for the other things that are needed.

[FarmPondFalcon]

Thanks very much! I appreciate this site.