Plumbing size opinion question

NeedMoreSun

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When I bought our new house I didn't like any of the equipment, much of it was on the last leg, and so many plumbing leaks I simply poured a new pad and started 100% new, as well as a little further from the pool so noise and sight hidden just around the corner of the house. I went with all 2" PVC based on reading input here, as well as in the past having a reef tank where every bit of flow saved was a plus.

However, in regards to a pool I'm questioning the usefulness at least with my current configuration. Everything was 1 1/2" when I moved in, so everything below ground still is. Main drain dedicated line, two skimmers that tie together to a single line somewhere, two returns tied together, and one dedicated pressure return. Depending on which one they run probably 30-40 feet. At the pad everything goes to 2", the main and skimmers converted to 2" before the Tee tieing them together.

However, the sand filter has 1 1/2 inch fittings so it has to get necked down and then back up there. I'm now starting to prepare to plumb in a new heat pump and it also has 1 1/2" fittings so it will need to be necked down again. So, with everything underground at 1 1/2 and now two places even on the pad where it has to be reduced to 1 1/2" am I really saving that much trying to stick to 2" where I can other than a little more expense for fittings and making the work of plumbing a little more difficult? I understand there is less friction loss, but with it being such a small fraction of the total plumbing I'm wondering if the difference would really be measurable by anything other than a gauge or just a formula showing there's a minor difference.

If the pool itself already had 2" I'd likely worry more and even make more effort to avoid equipment that's not 2". I also have about 60 feet of 1 1/2" PVC and a box full of fittings in the garage and only 10 feet of 2", so before I run to Lowes I'm basically looking for opinions on if I should continue bothering with 2" for a small fraction of total plumbing. I won't be intentionally changing anything BACK to 1 1/2 that's now at 2", but just returning to using 1 1/2" when adding or making changes anyway. A whole lot easier for me anyway to cut right through 1 1/2 compared to 2" that barely fits into my PVC cutter :) Agree, or disagree that just friction loss difference probably isn't that big when most of the distance is already 1 1/2 anyway?
 
Most of your friction loss is in those fittings. Straight runs like most of your underground pipe aren't where the loss is. It's in those 90 or 45 degree fittings, and most of those are there at the equipment pad.
 
Thanks to both of you. First, I won't stress but the reminder on it being the fittings just triggered what I think I'll do. I always make sure I have unions before and after every piece of equipment and I've been using the 1 1/2 to 2 adapter right at the equipment. I'll stick with 2" for most but also not worry about leaving it at 1 1/2 right AT the equipment connections for just a short, straight distance and bring it to 2" on the other side of the union instead of right at the equipment.

What brought most of this up in my head is the design of the valve on my sand filter. The input and output connections are so close that if going to 2" right there the pipes almost touch. NOW I need an elbow to route to the heater and it won't fit. I'll just change that part to 1 1/2" but only a straight run as short as possible to get clear of the other pipe, add the union, and go to 2" before any other fittings.

LOL, I love a question post that in the end only needed a few comments to make me think straight :) Thanks again!
 
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