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Motorized Valves

Useful Tips and Conversion Tables

Here we have assembled some tips of wisdom on sizing your piping and fittings. You will find conversion tables, dimension tables and friction loss tables. We are always looking for useful information to help others with their plumbing needs, so e-mail us any tips or tricks you have. Good luck with your aquarium and we hope this page helps you.

Tip #1:
When sizing your plumbing, consider the friction loss in pipe table listed below. You want to ensure that you don't buy fittings, valves and piping larger than you need because that will cost you money you don't need to spend. On the other hand, if you size them too small, you will have so much friction in the plumbing that you will not get even close to the rated flow from your pump! The pump loss curve is an inverse square, so a little bit of friction drops your pumps flow by the square of the amount of friction you added.

Tip #2:
When you get a pump, look at the inlet and outlet connection sizes. Generally, most pumps have an outlet connection smaller than its inlet connection. This is so the pump can use velocity pressure relationships to its advantage.

If you are going to pipe the water more than 2-3 feet from the pump back into the tank, it is advised that you step up the piping to the same size as the inlet, or one size larger.  Consider the friction loss in pipe table.  So, within the first 9" or so after you come out of the pump, you will want to transition up to that larger pipe size.  This tip will get you the best possible flow from any given pump.  It should save you from buying a larger pump because of bad plumbing :)

Always keep the inlet piping to the pump equal to or greater than the inlet size of the pump. If you use smaller piping coming into the pump than the pumps inlet then you will significantly shorten the life of your pump!

Tip #3:
When using a gate valve to throttle flow locate a utility ball valve after the gate valve.  This will allow you to quickly turn off the flow through the gate valve without changing its setting.  This can save you many hours when you have pains-takingly balanced two opposing gate valves for your skimmer and tank return off the same pump!

Tip #4:
Place unions and utility ball valves on both sides of your pump.   (Or, use true union ball valves on each side.)  This way you can turn off the pump, shut the ball valves, and then remove the pump from your system for its monthly impeller cleaning.  The advantage of the true union ball valves is that they take up less space than the other combination and they are usually about the same price as buying a separate union and valve.

Tip #5:
Don't use tools with serated jaws to tighten threaded plastic joints. The serated edge of the tools jaws creates indentations with sharp edges. These indentations cause stress cracks that lead to leaks and plastic plumbing ruptures. Try using a strap wrench, or placing a piece of leather or thick rubber between the tool and the plastic fitting/pipe. I can't count how many times I have seen wet floors because someone did not know this tip. Please let us know if you have any questions or need some suggestions.

Tip #6:
When choosing a check valve remember that check valves are designed to prevent flow reversal. Not to guarentee that there will be no reverse fluid flow at all. There are special check valve assemblies that do guarentee that there will be no reverse fluid flow, but they are very expensive and are usually used in drinking water systems to prevent contamination. In an aquarium environment, the need is to prevent reverse fluid flow during maintenance and power outages. For this purpose the best check valves are diaphragm or piston check type valves. These valves will provide the best possible revese fluid flow protection available in a reasonable price range. Keep in mind that there most likely will be a very small amount of leakage past a check valve in an aquarium application. This leakage will be on the order of a few drops per minute or even none when a good quality check valve is used.

Tip #7:
If you use a fluidized bed filter on your aquarium, you can run into trouble if a power outage occurs. During a power outage the fluidized bed filter will be starved of oxygen and will start to produce acid. If your power outage was more than a few minutes, it is advised, that you flush the filter before using it on your tank. One way to flush the filter is to fill a buck with aquarium water and have the filter pull water from the bucket and return to the bucket for a while. This will flush the acid from the filter and reoxygenate the filter. It works best if you go through at least two buckets of water before reusing the filter.

Tip #8:
This one a fellow I used to work with taught me. If you ever need to bend PVC piping try this. Almost fill the piece to be bent with ordaniry sand. Leave about two inches of unfilled length; more if it is going to be a very tight bend. Plug both ends with wooden stoppers that are lightly seated with a hammer. Pre-heat your oven to 200 degrees F. (Note: During pre-heating the oven temperature can exceed 500 degrees F depending on your oven so you must pre-heat the oven before using it.) Lay the pipe on a piece of foil or a metal sheet and put it in the oven. Heat it until the pipe starts to soften. Carefully remove the pipe with hot pads or heavy leather gloves as it will burn you. Then slowly bend the pipe around a wooden mold to the desired shape. Clamp or block in place and allow to cool slowly. You can then empty the sand, trim up the piece and wash it. The sand keeps the pipe from collapsing during the operation, but you will probably still seem some reduction in cross sectional area when you bend the pipe. Now you know how the pros shape piping.

Tip #9:
Always use a screen on the inlet piping to your pump. Chunks going through your pump will damage the impeller and shorten the pumps life. If you are using a bulkhead fitting to pull water from your tank or sump then get one with a screen on it.

Plastic PVC Pipe Dimensions

Nominal Size Inches Actual O.D. Inches

Schedule 40

Schedule 80

Wall Thickness Inches Weight
Wall Thickness Inches Weight
1/4" 0.540


--- 0.119 0.10
1/2" 0.840 0.109 0.16 0.147 0.21
3/4" 1.050 0.113 0.22 0.154 0.28
1" 1.315 0.133 0.32 0.179 0.40
1 1/4" 1.660 0.140 0.43 0.191 0.57
1 1/2" 1.990 0.145 0.52 0.200 0.69
2" 2.375 0.154 0.70 0.218 0.95


Friction Loss in PVC Pipe


Feet of Head Loss per 100 Feet @ Diameter (Inches)

1/2" 3/4" 1" 1 1/4" 1 1/2" 2"
0.5 0.3 --- --- --- --- ---
1 1.1 --- --- --- --- ---
2 4.1 1.0 0.3 --- --- ---
3 8.6 2.2 0.7 --- --- ---
4 14.8 3.7 1.1 0.3 --- ---
5 22.2 5.7 1.7 0.5 --- ---
10 80.5 20.4 6.3 1.7 0.8 0.2
15 --- 43.3 13.4 3.5 1.6 0.5
20 --- 73.5 22.8 6.0 2.8 0.8
30 --- --- 48.1 12.7 6.0 1.8
40 --- --- 82.0 21.6 10.2 3.0
50 --- --- --- 32.6 15.4 4.6
60 --- --- --- 45.6 21.6 6.4
70 --- --- --- --- 28.7 8.5
80 --- --- --- --- 36.8 10.9
90 --- --- --- --- 45.7 13.6
100 --- --- --- --- 56.6 16.5
Example:  30 feet of 1" diameter PVC pipe carrying 20 gpm will produce:
(30 x 22.8)/100=6.84 feet of head loss due to just the total length of pipe used in this system.  Then you must still add in the elevation change, and the loss due to all the fittings and valves.


PVC Fitting Friction Loss in Equivalent Feet of Pipe

90 Street
45 Street
Out side
of Tee
thru Tee
1/2" 1.6 2.5 0.8 1.3 3.0 1.0
3/4" 2.0 3.2 0.9 1.6 4.0 1.4
1" 2.6 4.1 1.3 2.1 5.0 1.7
1-1/2" 4.0 6.3 2.1 3.4 8.0 2.6
2" 5.0 8.2 2.6 4.5 10.0 3.3
Example:  If you have three 1" - 90 elbows in your piping system, you are introducing:  (3 elbows x 2.6 feet) = 7.8 feet of equivelant pipe.  Add this length to the total length of your system, and use the previous table to figure out the amount of head loss introduced by the new total system length.


Conversion Factors for Units of Pressure and Head

(Multiply unit on left by factor in column.)

Pounds per square inch Pounds per square foot Feet in height of fresh water Feet in height of salt water
Pounds per square inch 1.000 144.000 2.3067 2.2504
Pounds per square foot 0.006945 1.000 0.01563 0.01563
Feet in height of fresh water 0.4335 62.428 1.000 0.9756
Feet in height of salt water 0.4443 63.9887 1.0250 1.000
Example:  To convert from 10 feet in height of salt water to pounds per square inch use the cross table above as:  10 ft x 0.4443 psi = 4.443 pounds per square inch.

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