Plumbing Questions

[Stephen1]

I am building a new home next to my Log Cabin. I have 1.1/4 ABS line coming up from the lake with a heated line in it from a submesrable pump, it is reduced in the cabin 3/4" before 3  micron filters, then a UV light then 2.5 gallon pressure tank. (i would like to put a tannin filter next) 
I would like to send water to the new place. It would mean sending the clean water 100' through 3/4" line. The new place has 1.5 bathrooms and a kitchen. I can add an extra  bigger pressure tank in the new place. Will I get sufficient water at the new place?
 If I send 3/4? and just install a larger pressure tank in the new place, will it pressurize from the smaller tank in the cabin? will it all be the same pressure with 3/4" line between them or will I see a lag in pressure between the 2 buildings. 

Is there a calculation to help figure this out like Electrical? 

The other choice is sending the water in a 1.1/4 line to the new place, run electrical over to a larger pressure tank switch and then move the filter system over to the new place. I would then send 3/4" line with clean water back to the cabin. I have a bathroom with shower and a small kitchen in the cabin. I could leave the small pressure tank in the cabin. 

[sprucebunny]

You will need a check valve between the two pressure tanks/systems. You should get enough water if your pump is good and you aren't going uphill too far.

[firefighter ontheside]

I would install a check valve in the new place to avoid pressure from the new tank being used at the cabin.  That is what I did when I used to share a well with my grandmothers house.  I had 1" plastic line running about 400 feet from her house.  Pressure was decent and we did not have a second pump, just the pump in her well.

[doc henderson]

we had 5 acres out in hays.  the well was on the east end of the property and house.  I had a 40 gallon PT in the well house and ran a one inch pvc to the house and on out to the shop with a T goin g in the house.  I put another tank in the shop.  so the house had a big pressure tank on both ends of the system.  we could shower, flush and run 2 zones of sprinklers and not see a drop in pressure.  the pressure drops when there is not enough flow, and the distance and size of the pipe affect flow.  

[YellowHammer]

You will certainly see a pressure drop in the pipe when the water is flowing. Bernoulli's equation shows that as the velocity in a pipe increases, the pressure will drop down the length of pipe as a function of restriction (head loss and friction) and flow.  The more the flow required, the lower the instantaneous pressure on the other end, however, under no flow conditions, the pressure will be the same.  

If you go to an on site pressure tank, or reservoir, then it will control the local pressure, but the refill time or tank recovery is still controlled by the feed pipe.  Kind of like a hot water heater.  You have as much hot water as you want until it is empty, but then the amount of hot water is based on its recovery capacity, in this case, the recovery being dictated by the feed pipe size, source pressure and accumulated head losses due to fittings and stuff. 

There are plumbing calculators to help you run the numbers down.  If you want to do the math, then every fitting and valve you install will have a Cv number that is used to calculate its head and flow losses.  Add all the losses of every fitting, bend, check valve, etc and that will feed into the flow loss equation and tell you what your calculated flow rate vs feed pressure will be in the pipe.  

The easier solution is to simply size the on site pressure tank bigger than you need, and never have to wait for it to recover. Sometimes those are relatively low pressure, so you can get a booster pump to bring the pressure up at a loss of flow rate.

There is a huge difference in head losses due to pipe size.  For example, a good rule of thumb is that every time a pipe size is doubled, it will carry 4 times the flow rate at the same pressure loss.  

Also, every 90 degree sharp bend in rigid pipe equates to approximately 10 feet of straight run.  So adding a few elbows is a big deal if the pipe diameter is marginal. 

If at all possible, run at least a 1" line between the two locations.