Yes, I saw that a couple of weeks ago. It says 10% improvement with two 45s and 20% improvement with the sweep. But then there are other articles on the internet that say that the two 45s are up to 10% worse! So which to believe?
Frankly, I don't either. My inclination is to trust the engineering based sources and references because they have been around a lot longer than some of these web sites and I have used similar sources throughout my engineering career.
But there maybe valid explanations for the differences as well. In this case, they tell you not to focus on the setup but the setup is critical in this type of measurement. You must be meticulous in your methodology or you cannot trust the results. The exit is a bit too close to the fitting and not representative of typical pool plumbing changes we are talking about.
Another potential problem with this type of test is that they say they are using "typical fittings" for the test but what I have noticed is there is no such thing as a typical PVC schedule 40 fittings. I have several different types on my equipment pad and solar that appear to have different radius of curvature. This will cause different head loss in the fittings since the geometry of the fitting determines the head loss.
As for other sources on the internet, part of the problem I see is the lack of documentation you will see on many web sites that post head loss numbers. Engineering ToolBox is one of these sites. It has great information but they do not source any of the information. If fact, they have a disclaimer on the site that says the following:
The content in The Engineering ToolBox is copyrighted but can be used with NO WARRANTY or LIABILITY. Important information should always be double checked with alternative sources. All applicable national and local regulations and practices concerning this aspects must be strictly followed and adhered to.
I tried to contact them about where they got the information for the fitting head loss but got no response.
I know everyone wants a simple answer to this but I do not think there is a simple answer.
But consider this. Even if the above test is true and there is a 10% benefit to 2x45, the pad fittings may be at most 10% of the total head loss in the plumbing due to the other plumbing and equipment which makes the total impact only 1%.
However, if you really wanted to have a major impact on head loss, forget about the 45s and just up size the plumbing. Going from 1 1/2" to 2" reduces the head loss in the pipe by 71% and the fittings by 63%. That is a much larger impact than messing with fittings.
