The fact that most charts didn't support it was the first clue that I was about to do something drastically wrong. Q: Leaf basket? Does that figure in the flow equation? Nothing I saw mentioned that I should calculate friction loss on the inflow side. *sigh* The list was just a quick off the top of my head thing. Now that I see how much of a difference the diameter of the pipes make, I am going to redesign stuff since I have to get all new fittings. Basically I have a ball joint shutoff on both the intake and outflow, and a quick disconnect joint on the pump side of both (least I thought about that!) I am using threaded connectors just in case I ever need to replace pieces. So on the outflow side I have: pump to... - male adapter - (threaded to pipe - This will now also expand the 1 1/2 threaded to 2" or greater pipe). - a 90 bend - another male adapter (pipe to threaded) to screw into the quick disconnect coupler (QDC). - A QDC -2 threaded adapters (I could not find a nipple at that size.) to connect the other side of the QDC to a ball valve - (gate valves were brass only and much more expensive) - another male threaded adapter to pipe - a "Tee" - straight run is 1 1/2 with a side discharge of 1/2" (This is for a little circulation jet I thought might help to circulate bottom water to the bottom drain) - 16' of straight pipe - 90 bend - 1' pipe - 90 bend - 2 ' pipe (static head) - 90 bend - 1 ' pipe to outlet yet to be figured out. On the intake side I have: - Skimmer basket with 4 " pipe - 90 bend - ~10' 4" pipe - 90 bend - short run to a filter box. (yet to be figured out) but approx 2'w x 1.5'w x 1.5'd - with some type of filter materials Maybe pvc ribbon or scotch-brite pads or ??? I also have a bottom drain that will be connected to the filter box and it uses: - ~ 15 feet of 4" pipe - 2 45 bends - 2 90 bends I have not made provisions for valves to adjust flow from the skimmer and BD but figure I can add those later on the inside of the filter box if needed (or I can stuff a rock in one to reduce flow, lol) From the filter box to the pump, I probably will run either 2 - 3 " pipe, no decision made yet about 5 feet. - I'll need a reducer from the 2-3" pipe to 1 1/2" - pipe to threaded male adapter - threaded Shutoff ball valve - 2 threaded adapters - Quick disconnect coupler - 2 threaded adapters and the pump. The one headache I have is trying to reduce the size of the pump box. I did not get the self priming pump, so I am setting the pump below water level and I need to house all the disconnects and valves so it comes out to about 3' square. That's a pretty big ugly box to have sitting there. I did realize that I can run the outflow side parallel to the intake and that would reduce the width of the box to 1.5' or so, so I may do that, but it means an extra 90 bend. I could also place the pump box under the deck and build a access door, but that would add another week of work. *sigh* Last option is to put it under the deck with no trap door and I could crawl under there to pull out the pump for winter.. ugh. I suppose I can locate the valves remotely, but then I have little boxes all over.... Decisions, decisions.... This is fun right? Poppa

The concept of pressure as it relates to the residential water distribution system is without question the most miss-understood topic in all of plumbing. We constantly see questions posted regarding pressure and invariably someone will suggest going to Lowes or Home Depot and getting one of the little pressure gages with a hose thread attachment, then measuring your line pressure, as if that would yield any usable information. In truth, those gages only read "Static head pressure" which is the pressure on the system when all valves and faucets are closed and there is no flow, however, the performance of your showers or fixtures is dependent upon "Dynamic Pressure" or what is more commonly known as "Working Pressure" or "Flow Pressure". In order to effective measure dynamic head pressure we would need to install a Tee at the point where the fixture is attached to the water distribution system and measure the line pressure as the water passes the gage and into the fixture. IN one of my previous posts I described how the static head pressure on the municipal main can vary by changes in elevation. The same is true of the water in your house distribution system. Let us consider a two story house where the water main is located near the floor in a basement. While we may measure 45psi static head pressure at the main we must remember that the water will loose 0.434psi per vertical foot of rise. This loss is technically defined as "Vertical Static Head". In addition to vertical static head we must also consider the "Friction head loss" which results from friction between the moving water and the internal wall of the pipe. Thus "Dynamic Head Pressure" can theoretically be estimated by computing the vertical static head loss and the friction head loss, then subtracting the losses from the static head pressure at the main. let us put this in perspective. Imagine a house where the water enters the basement 1' above the basement floor and the basement has an 8' ceiling. We have a 7' rise to the ceiling, then a 1' rise for the floor joists and flooring material on the 1st floor. Now let us assume the house has 9' ceilings on the first floor and another foot for the floor joists to the second floor. We then have another 6' rise from the 2nd flr floor level to the shower head so our combined vertical head loss is (7'+1"+9+1'+6") x 0.434psi = 24' vertical x 0.434+ 10.416psi vertical static head loss. This means that if you had 45psi static head pressure at the main you would have 45psi - 10.41psi vertical static head loss = 34.59psi at the shower head. From this we must then deduct "Friction Head loss" however, computing friction head loss is not nearly as simple as computing vertical static head loss simply because as the velocity of flow increases on a pipe, the friction head loss will increase proportionally. now let us imagine that the water main is at the front of the house but the master bath is at the rear corner where we would have a 50' horizontal run of pipe plus the 24' vertical rise for a total of 74' of pipe. If we were to be precise we would need to also compute the fitting insertion loss for each fitting on the run. By example, a 1/2" elbow has a fitting insertion loss equal to .9 feet of pipe. W could compute all the fitting losses or we can rely upon the code approved standard of allowing an addition 20% for the pipe length. Thus our pipe length is now 74' + 20% = 1.2 x 70= 84'. Now let us imagine the we have a 1/2" copper pipe running directly from the main to the master bath. Now let us consult the copper pipe friction head loss table. In a 1/2" copper pipe with a flow rate of 1gpm the friction head loss is 0.008psi per linear foot of pipe thus the friction head loss to the master bathroom at a flow rate of 1gpm would be 84' x 0.008psi= 0.672psi. Not enough to really be concerned with, but let us examine what happens if we turn on the shower at 2.5gpm and the lavatory at .5gpm. The flow is now 3gpm and the friction head loss is 0.161psi per foot x 84' =13.54psi friction head loss. In this example, even though we had the code minimum 45psi static head pressure at the main, because the line was improperly sized to the master bath the resultant "dynamic head Pressure" at the shower would now be 45psi minus (10.41 vertical static head loss + 13.54psi Friction head loss) or 45psi - 23.95psi loss = 21.05psi. Even this would not be a big problem for conventional shower mixers because they are rated to perform with a minimum of 8psi and a flow rate of 3gpm, however, we commonly hear complaints from homeowners that they did a remodel on their bathroom where they removed a conventional mixer and replaced it with a pressure balancing mixer. A pressure balancing mixer requires a minimum of 20psi dynamic head pressure at a flow rate of 3gpm. From our example you can see that the new shower mixer requires 20psi while we only have at best 21.05psi available. Needless to say, if anyone were to run water anywhere in the house, the resultant pressure to your pressure balancing mixer would not be sufficient for it to operate properly, and sadly enough, most people get on the phone to the mixer dealer or manufacturers complaining their product is no good. Please believe me when I say, there is no guesswork in plumbing and although you may feel confident that you will save a pile of money by doing it all yourself, this is a prime example where you really should consult the services of a plumber, if for nothing else but to plan your layout. This is also why in most jurisdictions you may perform maintenance on a system without pulling a permit, but all new work, whether it is building a house from scratch or simply doing a major rehab requires all the proper computations and pulling a permit before the work may commence.

Pressure loss due to elbows is not the only issue you are potentially dealing with here. On their own, the additional elbows in the pipe will not cause any noticable pressure loss. However, when water flows through an elbow, the flow pattern is disrupted significantly and needs distance to smooth out again so as not to cause problem in your shower valve. For this reason, shower valves will specify the minimum length of straight pipe necessary before entering the valve. You need to look at the specs for your shower valve to ensure the last elbow is far enough from the valve. Otherwise you will have a problem with sporatic flow, the showerhead spitting water at you in spurts, inability to control temperature, all generally unpleasant, not to mention potentially damaging to your valve. As to the membrane davidro1 referred to: Waterproofing. You must have some waterproofing mechanism in a shower installation or it will leak into your walls. Wonderboard IS NOT waterproof.

Many people measure the static pressure at the point where their water line enters the structure and erroneously assume that the pressure should remain constant throughout the structure when the water is flowing, but such is not the case. Static pressure is just what the name implies, the pressure when the system is static, or in laymen's terms, when the system is at rest with no flow. The moment flow begins the static pressure will instantly drop to "Dynamic Pressure" (working pressure), which is static pressure minus "Vertical Static Head Loss" and "Friction Head Loss". Water physically weighs 0.434pounds per vertical foot column therefore if we pump water up hill we lose 0.434psi for each foot of vertical rise, and consequently, if the point of demand is lower than the prime mover, such as a house connected to a municipal main where the house is downhill from the connection, we would gain 0.434psi for each foot of vertical differential. now while Vertical Static Head Loss is very simple to compute, "Friction Head Loss" (FHL) is another matter entirely. FHL is a loss of pressure and flow caused by the water physically rubbing the inside of the pipe walls and eddy currents or restrictions generated by fittings in the pipe run. If one wants to be technically precise they must have a list of all fittings in the pipe run, from the prime mover to the point of demand, then consult a "Fitting Allowance Table" to determine the fitting loss for each fitting. Fitting Allowances are expressed in the equivalent length of straight pipe that would represent the same friction loss. By example, the fitting allowance for a 1/2" copper 90deg elbow is .6ft. For simplicity when estimating FHL the code allows us a shortcut. First we determine the actual length of all piping from the source to the point of demand, then multiply that length by 1.2 to compensate for fitting allowances and yield TDL (Total Developed Length). Maximum volume of flow is determined by the size of the orifice in the valve at the demand point. Once we know the volume of flow and the TDL of the pipe we then consult a publshed Friction Head Loss table to determine the amount of pressure loss, which is either expressed in psi/ft or sometimes in psi/100ft. In addition to Friction Head Loss the table will express the velocity of flow for a specific volume in a given size of pipe. Velocity of flow is very important for two reasons, 1. the higher the velocity of flow, the higher the friction loss and 2. if the velocity of flow exceeds 12ft/sec in copper or or 15ft/sec in plastic pipe we end up with excessive pipe wall erosion, therefore the codes limit us to 8ft/sec in copper and 12ft/sec in plastic pipe. To give you an example of how it all comes together, under the IRC (International Residential Code) the minimum allowable static head pressure at the water main is 40psi however according to the specifications on IRC Table T 2903.1 the minimum pressure for a hose bibb is 8psi with a flow rate of 5gpm. When you add a conventional garden hose to that hose bibb, the friction loss in the hose is 2 to 3 times the friction head loss of an equivalent length of pipe. Adding to that, a hose nozzle and its easy to see why your flow is diminished.