Upsizing pipe size, worth the effort?

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B

BravoFour

0
Feb 4, 2014
1
Hello everyone,

The pool:
19x35 ~30,000gal grecian in-ground
two returns
main drain (deep end)
one skimmer
all the in-ground piping is 1.5" flexible pvc from what I can see
equipment pad is maybe 6' on a diagonal from the pool itself (not far at all)
1.5hp Hayward superpump (1 speed, 230v) on a timer
chlorine, no salt

I just purchased the house and along with it came the pool, a huge plus in my eyes. The filter is an old sand one and the multivalve went just prior to closing it this last year. To the point in which a whole new unit is necessary and not just a gasket (housing is cracked on the inside). I an upgrading to a Hayward DE4820 DE filter and getting the new mutlivalve to go with it. I wondering if upgrading all the above ground piping to 2" worth the effort?? Now its not that I'm lazy...far from it. I just always over think everything and I would rather do it right now when I have to redo everything that wish I had done it. It's not really a cost issue either. Just wanted to confirm all my reading on going with more flow, less pump.

Thanks guys!
Pat
 
:wave: Welcome to TFP!!!

I would recommend making the above ground pipes 2" while you are in the process of changing equipment. Most head loss is in all the fittings and turns (most of which is on the equipment pad). So, making them larger can increase the plumbing efficiency and thus increase the flow rate (which will also increase the amount of electricity that the pump uses BTW).

I would highly recommend going to at least a 2-speed motor/pump when the time comes to save yourself some $ on electricity.

Personally, I re-did my entire pad in 2" pipe when I switched to a smaller 2-speed pump to help maintain adequate flow rate for my solar system. All my in ground plumbing is 1.5" like yours.
 
When you say all the in ground piping is 1.5 inch, are you looking at the pad and determining this??? Is ALL the flexible PVC pipe exposed ??? Todays "norm" seems to be 2 inch PVC pipe. Without seeing any pictures, my guess is you really will not be changing too much pipe, other than the exposed pipe at the pad. If this is the case, I wouldn't bother. Just my .02
 
I disagree ... all the exposed pipe at the pad is where most of the 90 degree turns are ... and up-sizing these has a much greater influence than up-sizing a bunch of straight (or flex) pipe.
 
There is no max flow rate for a given pipe ... there are recommended flow rates, but no real maximum. So you can not just say 42 vs 73.

BTW, my pool has 1.5" pipe and I previously had a large Super II 2.25 HP pump on it with no cavitation problems ... that is real world that directly conflicts with statements in the link.

Sure the 1.5" straight pipe will add more head loss than if it was 2" straight pipe, but all that underground pipe is harder to replace. Why not up-size all the above ground turns and reduce their contribution to head loss? I think what you are missing is that head loss in cumulative and most of it is in the pad plumbing and equipment ... having one section of smaller pipe is NOT going to set a maximum on the flow rate. This can be seen from the fact that the eyeballs in most pools are only 1" diameter at most ... they add head loss but do not "restrict" the flow.
 
The link that you posted is completely wrong. I will give you the following for instance.
If you had a swimming pool plumbed in 1.5" pipe and tried to put a 2 h.p. full rated pump on it for circulation. You would actually put a stain on the pump due to the force of trying to move more water than the pipes are capable of moving. This is called cavitation which means that cavities or bubbles are forming in the pump.
Click to expand...
That is completely wrong. What would actually happen is there would be less load on the pump because of the increased head. The pressure would be higher but that doesn't mean that the pump is working harder. Also cavitation is caused by high suction head not discharge pressure. Cavitation can not happen in the scenario that they're giving. It would be more likely to happen in a system with larger discharge piping.

I don't know where people get their information!!!
 
An overly simplistic example:
Lets say your pad plumbing has ten 90deg fitting and 20 feet of straight pipe.

Using info here: http://www.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html
The equivalent length of straight pipe for 1.5" pipe/fittings would be:
7.5 feet x 10 fittings + 20 feet straight pipe = 95 feet of 1.5" pipe

For 2" pipe/fittings:
8.6 feet x 10 fittings + 20 feet = 106 feet 2" pipe

So how many feet of under ground plumbing does a pool have? Maybe 200 feet? If so you can see that the head loss of the pad is ~1/3 of the total.

Now look at http://www.engineeringtoolbox.com/pressure-loss-plastic-pipes-d_404.html

So, using 200' underground at 1.5" pipe and the pad listed above, lets assume a constant flow rate of 50 GPM (which is about what I get I think with my small pump).

The underground 200' of 1.5" would have a head loss of 28.8 feet
The 1.5" pad plumbing would have a head loss of 14.4*(95/100) = 13.7 feet
The 2" pad plumbing would have a head loss of 4.3*(106/100) = 4.6 feet

With all 1.5" plumbing you would have 28.8+13.7 = 42.5 feet of head
With the 2" pad plumbing you would have = 33.4 feet of head which is over a 20% improvement for little real expense or effort.

Now sure if ALL the plumbing was 2", the underground portion would be only 8.6 feet for a total of 13.2 feet of head which is nearly 70% reduction from all 1.5" plumbing, but with significantly more effort and expense.

Of course this is ignoring the head loss through the pump, filter, heater, eyeball, etc.

Another way to look at it @ 50 GPM:
A 1.5" 90 adds 1.08 feet of head
A 2" 90 adds 0.37 feet of head ... a 65% reduction

Just to add ... I would not necessarily advise people to go out and rip their pad apart and redo the plumbing. BUT, if you are already having cut and replace pipe for new equipment, then it certainly does not cost very much to go ahead and use larger pipe while you are at it.
 
I say go with 2" for the above ground piping. I am in the process of changing my pool equipment (replacing pump, filter, and adding a SWCG), and I figure that for my system changing from 1-1/2" to 2" pipe for the plumbing on the pad will save me about 8 foot of head loss @ 60 gpm. That's based on 6 elbows, 2 tees, and about ten foot of pipe. For me the head loss is just one factor. The other is that both my new cartridge filter (Hayward SwimClear 3030 - 325 sq ft) and pump (Jandy 1 hp 2 speed) are set up to use 2" pipe, and it is easier to put reducing couplings right at where the 1-1/2" pipe comes up from the ground than to figure out how to connect 1-1/2" pipe to 2" unions at the pump and filter. Also, the 2" pipe looks better.
 

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