# Need to check water figures

Solar Expert Posts: 201 ✭✭✭✭✭
It just occurred to me that the place I'm building my house, being on a hillside (north facing, dang the luck!) might be suitable for an elevated storage tank. Not sure on the altitude the tank would be over the house at this time though. As soon as the weather gets a little less crappy I plan to take the GPS and some marker tape out to start plotting things out. 8)

Anyway, I just need to make sure I understand what I'm planning here. I would be building a concrete water storage tank at the top of the hill. I don't think I'll be able to get full pressure off gravity alone, but the existing well is already on top of the hill so this makes things a bit easier on that part.

From what I've been able to find, each foot of drop is 0.433PSI, and standard city water pressure is 40PSI. So, in order to get the full 40PSI so I'd have the same water pressure as city folk I would need 92 feet of drop. I'm assuming here that a 92 foot supply line at a 45 degree angle won't get this, I'd have to have a 184 foot supply line at a 45 degree angle headed downward from the tank, correct? The tank will most likely be buried and will incorporate the full filtering scheme so that reduces height some. But, is my math here correct that I'd need a 92 foot drop in altitude only, that distance and angle wouldn't matter? If it comes to it I can put a pressure pump on the system, but would prefer not to if possible.

Also... would it be cost effective to have a rainwater catchment system that pumped water to this storage tank? Or would this be a waste of time? The land is situated off a 25,000+ acre manmade lake used to supply part of the local water supply (in fact, due to an error on the part of the Corps of Engineers I own part of the lake) so I don't imagine the well would ever go dry. I suppose an alternative would be to do rain catchment and just use it to water a garden, and since it wouldn't necessarily be potable water it wouldn't take nearly as much thought.

Re: Need to check water figures

From trig:
• Elevation = supply line length * sine (angle)
• supply length = Elevation / sine (angle)
• Supply Length = 92 feet / sine (45) = 130 feet
Note; a 45 degree slope is darn steep... Using my powers of internet metaphysics--probably much closer to 30 degrees..
• Supply Length = 92 feet / sine (30) = 184 feet
Which is the distance you think you will need...

Also, GPS's are not terribly accurate for elevation... A good altimeter (or GPS with altimeter mode) would probably be more accurate (I had an 1980's Casio watch that had an altimeter function... Was dead accurate when compared with my plane's real altimeter. Another pilot found the same thing too.

Of course--you could get 200 feet of garden hose/plastic hose fill it with water and put a pressure gauge on at the bottom... But every "guy" needs an altimeter or watch with a pressure altimeter. :cool:

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 9,276 ✭✭✭✭✭
Re: Need to check water figures

You may find that you house may work fine with 30psi. You will loose some head in your filter. I'm going with rainwater catchment, with ozone bubbler as filter, and a strainer, before and after the storage tank. Once you pump water from a well, and store in a tank, stuff will start to grow. If you pump directly from well, no sitting water, and it stays OK. Over size your pipe by 1/2", and use 45 bends, not 90's. That helps the flow too.
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• Solar Expert Posts: 5,433 ✭✭✭✭
Re: Need to check water figures

Under the idea of KISS. Let's start with the easy stuff. First street pressure ranges from as low as 5 psi (yes, I built a house with only 5 psi from the city once,, had to booster it) to ~100 psi. "Normal" house pressure might average 30-50 psi if you run from a pump. Anything above ~20 psi is going to be fine for almost any application assuming you have some volume.

90' of head gives ~ 40 psi regardless. What diminishes this is friction loss due to pipe length, pipe diameter, number of bends, radius of bend etc. While you can calculate all of these, in the real world, over size any pipe, reduce the number of fittings and elbows etc. Running 1" or even 2" line will reduce friction losses, and increase volume at the same time. (Remember, any filtering system will reduce pressure net/net.)

All that said, if you are designing a system with ~90' of head, pay attention to the fact that pipes will move as water flow is changed (valves, tees etc) and some thought to good design is important. Thrust blocks, slip couplings etc. I did a 2" line with ~ 50' of elevation gain over 1000' horizontal. I was stunned to realize that the line moved several inches as the pressure came on and off. Without either the room to move, or proper thrust blocking will tear it apart in a heart beat.

If you have ~20 Psi net/net you should be fine. Barring that, a simple pump and pressure tank to boost to whatever you need is pretty easy to do.

Tony
• Solar Expert Posts: 1,060 ✭✭✭✭
Re: Need to check water figures

Are you planing on offgrid? If you are ongrid you might consider Geo thermal heat. I would probably go for that myself if I didn,t have free gas. In North western Pa my daughjters all electric home had a \$260.00 electric bill last monrh and we have had a preety hard winter so far. Thier house about 2400 square ft. she does laundry everyday. Really nice in the summer too as it heats your water in the summertime when your air is on. Winter it takes heat out of the ground and summer it takes heat out of your house and puts back in the ground.
Suposed to be 5 to 6 times as effecient as an air heat pump is. Solarvic:D
• Solar Expert Posts: 593 ✭✭
Re: Need to check water figures

Lets not get too excited! About hydronic GSHP -

A GSHP (ground source heat pump) (sometimes called geothermal) has a COP of maybe 4. Their advantage will be in areas with cold winters. Then you only have to worry about ground loops freezing but a well based unit would not have that problem.

An ASHP (air source heat pump) has a COP of maybe 3 to 3.5 down to close to freezing temp. Going on down the backup resistance heating and defroster comes on and the power consumption goes up. Somewhere above zero deg F the COP becomes 1 - all advantage lost (forgot the exact number)

Those both depend on the delta T of the water across the unit.

The lower the output water temp When making hot water for the house (for either hydronic heating or dhw) the more efficient the unit is. One of the new heat pumps as a dedicated hot water heater has a COP of something lile 2.1

İf your elec bill is 100 USD with electric radiant heat then

- with an ASHP and a COP of 3 it would be maybe 33 USD

- with a GSHP and a COP of 4 the bill would be about 25 USD

- making dhw a 100 USD bill would reduce to 50 USD
• Solar Expert Posts: 1,060 ✭✭✭✭
Re: Need to check water figures
russ wrote: »
Lets not get too excited! About hydronic GSHP -

A GSHP (ground source heat pump) (sometimes called geothermal) has a COP of maybe 4. Their advantage will be in areas with cold winters. Then you only have to worry about ground loops freezing but a well based unit would not have that problem.

An ASHP (air source heat pump) has a COP of maybe 3 to 3.5 down to close to freezing temp. Going on down the backup resistance heating and defroster comes on and the power consumption goes up. Somewhere above zero deg F the COP becomes 1 - all advantage lost (forgot the exact number)

Those both depend on the delta T of the water across the unit.

The lower the output water temp When making hot water for the house (for either hydronic heating or dhw) the more efficient the unit is. One of the new heat pumps as a dedicated hot water heater has a COP of something lile 2.1

İf your elec bill is 100 USD with electric radiant heat then

- with an ASHP and a COP of 3 it would be maybe 33 USD

- with a GSHP and a COP of 4 the bill would be about 25 USD

- making dhw a 100 USD bill would reduce to 50 USD

Well at my area I should get a cop of a little more than 5 at a 50 degree water temp. and goes to around 4 at 30 degrees with a good quality 2 stage furnace. I was thinking of going that way because I was worried about my gas well going dry. Decided to take my chances and if it does then make the purchase. Was thinking of doing one as a back up in case I did have trouble at gas well. Now thinking I might get a ductless air with heat pump with the refrigiation unit outside. Solar Vic
• Solar Expert Posts: 5,433 ✭✭✭✭
Re: Need to check water figures

Wasn't the original question about elevation and head? Aren't we veering off a bit?

Tony
• Solar Expert Posts: 5,183 ✭✭✭✭
Re: Need to check water figures

Since you mentioned you are going to build, the pressure loss issue is one of the reasons plumbers are now going to one piece plastic piping as the bends now have very large radius's and do not drop the pressure as much as a copper elbow or T.

HTH
Eric

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• Solar Expert Posts: 593 ✭✭
Re: Need to check water figures

All GSHP ground loop or loop into the well pipe should be HDPE or equivalent - best is fusion welded.

What manufacturer sells this GSHP with the COP of 5 anyway?
• Solar Expert Posts: 1,060 ✭✭✭✭
Re: Need to check water figures
russ wrote: »
All GSHP ground loop or loop into the well pipe should be HDPE or equivalent - best is fusion welded.

What manufacturer sells this GSHP with the COP of 5 anyway?

Water furnace model invision nd-038 Low speed ewt 50 = 5.11 ewt 60=5.64 ewt 70=6.15 ewt 80=6.58
ewt90= 7.01. ewt40=4.58 ewt 30=3.99 ewt 3.42. @8 Gal min. flow. Climatmaster tranquility has similar rateings. In my area the ground temp is 50 degrees. My back yard is wet (next to a swamp) so I think I could keep the circulating water temp close in the 40 degree range if I didn,t short loop like some installers do to make the big buck. Since I have a gas well that gives me free gas I won,t be doing it.
• Solar Expert Posts: 201 ✭✭✭✭✭
Re: Need to check water figures

Yes, this veered way off topic, but I don't mind. On the heating I'm probably going to use a gas fired water heater with radiant heat to begin with, with solar heated water to come at a later point. No idea on air conditioning yet, not too worried about it right just yet.

Not too worried about the water purification and critter prevention at this point, just looking for information on the initial design. I'll investigate purification methods once I decide how supply will take place.

I don't know if I'll make it 100 percent offgrid to begin with, but that is the goal I'm shooting for.

So (thanks to BB) what I'm gathering here is, if I want 40PSI with no booster pump, I'm not necessarily going to need a 90 foot altitude drop, since the sine doesn't quite add up to the expected distance? The land isn't a 45 degree angle drop, more like a 20-25 degree average (some steeper, some shallower) but I went with 45 degrees as a means of getting my mind around the concept. I definitely like your calcs better than mine, since it only added 40 feet for a 45 degree angle vs 90 degree angle. That makes this MORE likely to happen .

Hmmm... guess I need to get a pressure tester to see what my current house has because what I have now is what I want. I kinda get the feeling that I'm going to be having to do a pressure pump though, I don't think I'll have enough drop unless I build a lot lower, and that negates the whole reason of selecting this property to build on. I'll have an interesting view of the river feeding the lake where I'm at because the river snakes right before it hits the lake.

I understand about the water friction and elbows reducing flow, and I'd already planned to oversize the line. Anyone know how much of a pressure drop can be expected on say a 2 inch line with a 45 degree and a 90 degree bend? I'm also assuming here that line friction is built into the .433PSI/foot drop figure. Never heard of line movement with flow though. Is this going to be a real issue on a line that's solidly buried 4-5 feet deep?
• Solar Expert Posts: 5,433 ✭✭✭✭
Re: Need to check water figures

Telco,

Friction loses are fairly easy to calculate: http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html If you have better math skills than I. A 2" line with a couple of bends isn't going to drop pressure very bloody much.

As for pipes moving, you probably have to consult someone with a bit more civil engineering. What I do know from experience is that water lines move, and indeed move a lot depending on head and design. The idea behind thrust blocks (which are in essence large/massive usually concrete blocks that back up a pipe where it changes direction such that the pipe is forced against the block preventing movement. Personally, if I had ~90' of head, I would land the bottom of that pipe against a block where it turns to go into the house.

Tony
• Solar Expert Posts: 201 ✭✭✭✭✭
Re: Need to check water figures

Good deal, thanks Icarus. I'll add this to the long, long list of tasks to accomplish. Gonna get there one way or another.