Water supply / pressure problems - suggestions?

[_RaT_]

ByronBob, the other thing not yet metioned is that the smaller the pipe for any length means a higher water velocity for a given GPM. This creates a situation that can ge damaging to electric valves, 90's, tee's and even to the pipe itself in the event of valves closing sudenly.

 

[Caddyshack]

Hey everyone, thank you for the posts thus far.

OK.. So my pipe size stinks.... Still, I might be dense here but since the water company's feed to the manhole looks only to be 3/4 inch metal, how can my 1 inch plastic pipe be the limiting factor? Is it just the resistance the pipe provides to the volume of water being pushed? I understand that a larger pipe would not provide the same resistance per the volume of water moved.

Anyway, let us make the assumption that the wife won't let me trench up the lawn to put in a new pipe. /forums/images/graemlins/mad.gif Even that would not solve the problem of the frequent utility interruptions. So....

Could I put a couple of those 120 gallon retention tanks in series followed by a pump to a bladder tank connected to the house supply? Do those retention tanks handle pressure so I don't need a valve to shut off the flow from the municipal feed when they are full?

Are there downsides to this?

Having 240 gallons on tap along with the water in the bladder tank would sure mitigate the problems related to utility outages.

Thanks again.. Ron

 

[NY_Yankees_Fan]

Ron,

At 10 gpm flow, this would be say a shower and filling a washer, you would loose 55.5 psi for the 1500 feet of pipe. This does not include the loss of pressure through the water meter, valves, difference in elevation, etc. If the street pressure is day 60 psi, you can see you will have less then 5 psi on your end of the line.

When you only flow say a shower the flow is perhaps 3 gpm, the more flow the higher the loss of pressure. Based on the table Rat included in his post, for schedule 40 plastic pipe at 1 gpm the loss is .03 for every 100 feet, at 5 gpm it is .66, 7 1.24, and 10 gpm 2.40, as the flow increases so does the friction loss through the pipe.

As far as putting in the tanks, I will leave that for others, but it sounds like a fix. It would mean less tractor seat time /forums/images/graemlins/mad.gif
and not as much fun as digging a 1500 foot trench 3-4 feet deep. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[_RaT_]

There is a difference between 120 gallon tanks and 120 gallon pressure tanks. Much of a pressure tank is air. You will not be getting 120 gallons of water. TO call it a storage tank is really not quite accurate. It does indeed have water in it, it's purpose is not to store water so much as pressure. In situations where there is an inadequate supply of water, an in ground tank is used where we are. The cold climates will probably be different. On a well with 2 or 3 gpm, we are required to install a tank. The tank is usually around 3000 gallons. In it is a pump to supply the domestic water. The well pump keeps the tank full via a float switch. It has 24 hours a day to keep it full.

It is not unusual to have a 3/4" tap to the water utility line. Again, look at the water friction loss chart. It will show you the PSI loss for 100' lengths of pipe in a given size and material. 6' of 3/4" pipe at 60 PSI may well provide you with 30+ gallons per minute. 1000 feet of the same pipe will drop the pressure drastically and definitely drop the GPM by a considerable amount. Change the run at the 3/4" utility tap to 2" or larger (depends on overall length) and the PSI drop will be almost negligible. Pressure is close to the same, GPM is similar as well.

 

[ByronBob]

I don't know if a pump would allow you to have pressure on both sides of it. For example a well pump draws water on one side of it to pressurize the other side. It uses a one way flow control valve to shut off the water flow when it's not needed. If you put a pump in and there was pressure on both sides of the system I don't know if you can do that.
Another thing that water companies bark about is modifying water supply in this method. The tanks would give you more volume but no more pressure.
I don't know the answer to this question per se but my tank in the basement which is 120 gallons is made out of fiberglass resin and will handle at least 100psi. Very lightweight and strong.

 

[_RaT_]

Not sure what your asking. If your pump has a supply with 60 PSI of pressure, thats a bonus. You want a pump to have a supply pressure, some require it. On the outlet side of the pump will be a check valve. Most water companys will require you to install a double check valve prior to supplying water to the pump.

 

[DaveNay]

</font><font color="blue" class="small">( 6' of 3/4" pipe at 60 PSI may well provide you with 30+ gallons per minute. 1000 feet of the same pipe will drop the pressure drastically and definitely drop the GPM by a considerable amount.)</font>

I am certainly dense on this topic, because this doesn't make sense to me.

How can the GPM change due to the length of the pipe? I understand that the pressure will drop, due to friction with the inside of the pipe, but water is an incompressible substance, and if the pump is putting 30 gpm into one end of the pipe, then 30 gpm has to come out the other end. /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

Is this loss of gpm what causes a fixed displacement pump to burn out? Is this what is meant by "Head pressure"?

Just looking to understand what this all means.

Thanks,
Dave

 

[BobReeves]

Not sure what this relates to as I have no idea about GPM and water pressure other than... If I am in the shower and somebody flushes a toilet do I get scalded.

We are 900 feet from our meter with 3/4 PVC put in by the previous owner. From what everyone is saying this can't possibly work but our water pressure isn't any worse than I have experienced when we were in town. Ya if the wife flushes the toilet while I am in the shower the water gets a little warmer but not bad enough for me to even think about replacing 900 feet of water line. I would be tickled if it was 1 inch. Not sure why it's working as well as it is unless we have some really high pressure at the meter.

 

[_RaT_]

The pump may be capable of 30 GPM with no head, but if it has a head pressure, that figure will change. Water pumps can be put into a situation of zero GPM, the pressure will go to the maximum the pump can produce. They are not like the fixed displacement gear pumps used in tractors to pump hydraulic fluid. In a centrifigal pump, that may about 30 to 90 PSI depending on the design. In that situation, the impeller will simply spin in the pressurized cavity. It will eventually heat the water sufficiently hot enough to collapse the threads of most PVC fittings. In a well pump, you can have multiple stages that continue to feed each stage an increase in pressure. It's not unusual to see these pumps go well over 200 PSI. The GPM on your well pump will depend on it's HP and of course, the head pressure. A 3/4 HP pump with zero head may be able to pump 25 gal/min but placed in a well 300' deep with a head pressure of 150PSI just to get it to the surface not to mention pressurizing the system, it won't give you 25 GPM, it will be something less then that. Look a t a pump manufactuers web site. It gives the GPM for a given pump based on head pressure.

 

[ByronBob]

Look at it this way. Try blowing water through a garden hose and then try blowing it through a straw. You could have 60psi set up for both but the size of the line restricts the water pressure. And just like electricity water looses pressure by length away from it's source.