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Article 13: Pond Plumbing - Pipes and Hoses, by Jeff Richardson

Posted by Jeff Richardson on

The unseen component linking all your water features together is often times treated as an afterthought.  This needs to be as important as choosing a pump or filtration system.  Let’s talk about options: 

Pipe Materials: In broad terms, there are rigid pipes and flexible pipes (hoses).  Due to cost and corrosion, it is NOT advisable to use metal piping – stick with plastics.  They are easy to cut, come in a wide variety of sizes and matching fittings, and even come in different colors.  Most widely available are PVC (usually white or gray) and ABS (black).  Some sizes (like 1-1/4 or 2-1/2) do exist but are not readily available (especially fittings).  Go with the more common sizes and round up to the larger size if you are on the fence.  When it comes to large diameter hoses such as Liquatite (a PVC hose), this can eliminate many fittings and make very graceful turns rather than rigid pipes and fittings to make changes in direction.  Remember, smoother and graceful is what you are striving for in your plumbing system to maximize flow and reduce backpressure.  

Sizing Plumbing: It might seem that two 1” pipes carry the same volume of water as one 2” pipe – this is incorrect.  In fact, you need four 1” pipes to equal the cross-section of one 2” pipe!   But this is not the whole story.  Within the same plumbing system with the same head pressure, the velocity of the water is less in the smaller pipes.  Why?  A larger pipe has more volume of water flowing in its center unimpeded by friction.  This is a sliding scale; the smaller the pipe, the less volume at its center flowing unimpeded.  The chart below shows equivalent pipe sizes needed for equal flow.  It also shows the comparative added backpressure between sizes.  For example: Looking at the 1” column, 6 pipes are needed to achieve the same flow rate as one 2” (both with the same head pressure).   Although four 1” pipes equals one 2” pipe in cross-section, the 30% additional backpressure slows velocity in the 1” pipes requiring 5.7 pipes (rounded up to 6).  Note the GPH rating for the different pipe diameters.  MOST pond systems will be rated as LOW GPH flow.

Upsizing Plumbing: Using the chart above, you can see that flow rates of different diameter pipes you can expect.  A pump will have a flow rate and a certain diameter discharge.  Sizing your pipes to match this may be a mistake.  Once you add in the head and back pressure, you may permanently restrict the flow rate.  There is absolutely nothing wrong with using a larger pipe diameter (even if your pump has a smaller discharge – just use a bushing).  You will “future-proof” yourself if down the line you want or need a larger component or pump.  This way your plumbing system will always have enough flow for any eventuality.

Previous Article: 12: Pond Plumbing – Hydrodynamics

Next Article: 14: Pond Plumbing – Fittings

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