In ground pool plumbing


New member
Jun 14, 2010


Well-known member
Oct 17, 2009
WoyWoy Australia

I think two 45 joined to form a 90 would give less resistance as the angle is not as sharp more curved but it probably would be much unless you had a of of 90 in your plumbing .


TFP Expert
LifeTime Supporter
May 10, 2010
SW Louisiana
Yes, sweeping curves are better than sharp corners, just make sure you have pressure type PVC fittings not the shorter glue joint drain DWV type fittings (45's are a lot more common in dwv). I had to jackhammer up the concrete at the corner of my pool earlier this year because someone used a DWV elbow fitting on the return line (it lasted for 30 years almost to the week before blowing out).



Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Mas985 has done the math but I can remember that he has said many times that 2-45's simply aren't worth it. Use the 90's.

If you would liketo reduce the resistance in your system AND make a better pool, I would suggest purchasing a filter that's a little larger than normal.....around 125% or so of your pumps gpm. That'll more than make up for all the resistance within the 90's and give you a better system to boot.


TFP Expert
LifeTime Supporter
May 3, 2007
Pleasanton, CA
An isolated 45 has a little less than half the head loss of a 90. However, if you put two back to back it can actually be more than a 90 because of the interaction between the fittings and the fact that you have twice the glue joints. So given the uncertainty as to how it would actually work in a real installation, I generally do not recommend back to back 45's or at best indifferent. They take up more room too.

As for swept 90s, if you have a lot of 90s it may be worth it but I remember seeing a pad with nearly all swept 90s and it was a real mess. They take up a lot of room so the lay out tends to be really messy. Underground would be fine though.

My usual recommendation is that upsizing the pipe diameter is a far better choice than dealing with special fittings.


Jun 8, 2010
Just use the fitting that gives you the tightest group!




LifeTime Supporter
Feb 8, 2009
New Jersey shore
That retun line on an angle isnt a great idea... didnt read everyones post so that may have already been said. But once you back fill, the dirt may "push" on that pipe and cause major problems. I would come out of the pool wall a few inches, into a 90, then straight down to the ground.

P.s, holy glue joints batman