On plumbing, deep heaters, and lines

[jimim]

i have no 45's or 90's. all my plumbing was heated and swept for turns. the only time there is a break in my PVC is if the piece needed a coupler due to run length. i know a lot of builders seen here uses 45's but a lot also heat and bend. it just takes some skill. you can blow a line out pretty easy. i saw it done on my build when senior was teaching his grandson who will be one day running the show how to heat and bend and he blew a line out. i was there laboring most of that day to help with digging and there deff is some finesse to the process.

i think you will get answers both ways are ok. which is better. i would say less physical connections is better cause it's less failure points, but that is if the guy who was heating and bending knew what he was doing i would say.

to edit. . . i have bends coming up from the ground at the stack of equipment, but everywhere else sweep bends heated.

jim

 

[manoweb]

I did not know the bending technique.

 

[jblizzle]

IIRC, using two 45 fittings is actually more headloss and flow restriction than using one 90 fitting. So, that is a mark against that pool builder's knowledge in my book.

 

[manoweb]

But again the building department thinks otherwise, at least for drains. I will do further research

 

[manoweb]

I have found a number of tables that indicate there might be a moderate to great advantage in using 45deg elbows over "sharp" 90deg ones...
PVC - Friction Loss in Fittings and Equivalent Length

At 2.5" pipe diameter, a 90deg elbow introduces an equivalent of 8.6ft of pipe, two 45deg introduce 5.2ft... plus there might be a shorter run of pipe between the two because it goes on a diagonal. This said, I am not sure how important this is and how common is this solution for swimming pools

 

[Catanzaro]

Less resistance in any plumbing is better. Maybe 45* would be better, but when they built my pool, there was no way around 90* elbows. I have 2" plumbing and the return flow to the pool is powerful, even with 8 returns and 6 pool returns. The steps, I just ordered new straight returns for more pressure as these were not powerful enough.

Mas and some other members would be better at answering these questions, but I think the key is to make sure that the whole system is balanced, from the plumbing, filter, pump, size of piping, etc. Not just about elbows. Some pools would require separate pumps, even for your basic stuff or not everything could be on at the same time.

 

[PoolGate]

This is talked about in aquarium keeping all the time. 2 45s is always better than 1 90 for flow. For your pool, with such a powerful pump, would you notice any difference? In any case, if your plumber is willing to go all 45s I don't see why not.

 

[jblizzle]

I know this question has been discussed before on the Forum. I think using two 45s is so close to using one 90 that it really makes no difference in the full picture. The only additional consideration is that you double the amount of joints which could potentially become leaks when using the 45s.

 

[mas985]

I have found a number of tables that indicate there might be a moderate to great advantage in using 45deg elbows over "sharp" 90deg ones...
PVC - Friction Loss in Fittings and Equivalent Length

At 2.5" pipe diameter, a 90deg elbow introduces an equivalent of 8.6ft of pipe, two 45deg introduce 5.2ft... plus there might be a shorter run of pipe between the two because it goes on a diagonal. This said, I am not sure how important this is and how common is this solution for swimming pools

There are quite a number of errors in that table so I would be careful. The Hydraulics bible is the Crane TP-410 technical paper and they say that two 45s are the same as a single tight radius 90 (R/D =0.5). However, most PVC 90s are not exactly tight radius 90s and usually have a R/D of 0.75 vs 0.5 which means that the 90 could actually be less than the 2x45s.

Second, those head loss numbers are for isolated fittings and if you put two fittings back to back, the head loss is likely to be higher that 2x so you may end up with more head loss.

I would just assume that they are the same and that you will not get much benefit from dual 45s unless it is easier to plumb with the 2 45s and can reduce pipe length.

 

[manoweb]

I do not know, it was just one of the PB to claim they only use 45deg ones, and the table I linked is not the only one I've found that says a 45deg elbow has 5 times less head loss than a 90deg one. It seems reasonable if you think about it and well yes, for it to work I reckon the elbows need to be at a fair distance, not back to back obviously.

It was just a curiosity, it seems plenty of Pool Owners are satisfied with 90deg connections.

Now, I've seen some people run 3" pipes. Any reason they should or should not be used on a new pool (no spa)? I do not think the increase in cost is huge in the grand scheme of things...

 

[jimim]

99 percent of he builds on here use 2 inch. Even 1.5 for returns but always 2 inch for drains and skimmers.

I’m confused on what u r trying to accomplish? I would say if u use 2 inch all around and they minimize bends with heating and use 45 or 90 when needed.

 

[Catanzaro]

I have 2" plumbing all around. 90* bends (not sweeps), at least in the pool. 8 returns (4 on each side) that are T off at the base in concrete. Then the runs are to the equipment pad. The skimmer(s) have 2 separate runs (no T connections as they used 2" flexible piping). The main drain has 2 90* bends and a T back to the pad. Length is at the 60-90 foot runs, possibly a little longer. At the pad, I have your typical 90* bends and sweeps with 3 way shut off valves (Pentair). 2 HP pump and 350 lb. sand filter. I can tell you that this is plenty in terms of turnover.

Before I had the heater, the pressure was at 12 psi. After the heater, the pressure increased to about 22 psi. Still, the water coming back into the pool is plenty. Use sweeps where possible. Do not try to overthink this, as the calculations are complex and very few people, even on the forum will be able to provide you scientific answers. Mas, IMO, is one of the best. Thanks!

 

[mas985]

I do not know, it was just one of the PB to claim they only use 45deg ones, and the table I linked is not the only one I've found that says a 45deg elbow has 5 times less head loss than a 90deg one.

Like many things on the web, garbage keeps getting propagated. They all just copied the info from themselves. But unless it is sourced information, you really don't know where it came from or how valid it is. Like I said before, the most widely used source in hydraulic engineering is Crane TP-410.

It seems reasonable if you think about it and well yes, for it to work I reckon the elbows need to be at a fair distance, not back to back obviously.

Does it? A 45 is basically a 90 cut along the diagonal with an additional glue joint. So two 45s have the same total bend and the same radius bend as the 90, but 2x the glue joints. So to me, it is more logical that 2x45s have more head loss.

Now, I've seen some people run 3" pipes. Any reason they should or should not be used on a new pool (no spa)? I do not think the increase in cost is huge in the grand scheme of things...

Unless you will be running a spa, I would not recommend 3" pipe. You have to remember that the pipe and fittings are only part of the head loss in a pool plumbing system. Skimmers, drain covers, returns, filters, heaters, valves all have head loss and in most cases will dominate the total head loss over the pipe. So in many cases going from 2" to 2.5" is a small reduction in head loss and going to 3" hardly changes at all because a large part of the plumbing doesn't change with pipe size.

Also, while reduction in plumbing head loss does improve flow rate and sometimes by quite a bit, it comes at a cost of more energy use by the pump, unless you have a VS where you can reduce RPM to compensate. Also, flow rate is less important than what you probably have read from the internet (e.g. turnover). Pump run time is not all that related to flow rate so doubling the flow rate may not mean that you can run the pump half the time or visa versa. Many people find they can run on low speed of a two speed for the same amount of time as high speed and the pool is just as clean. But energy use 1/4th as much.

BTW, what type of cleaner are you planning to use? Anything other than a robot will force you to use your main pump and usually at close to full speed negating a lot of the gain of the larger pipe.