Looking for PVC fittings head loss charts

[mgianzero]

I'd like to remove any unnecessary check valves (or use 2-1/2" inlets instead of 2" inlets) so as to improve my circulation flow rate. (I've already removed a few unnecessary 90's and the pool heater with dramatic results!)

However, I've heard that check valves can cause a significant head loss on any system (I have the Jandy no-lube type). Is this true? Where can I find a place which lists typical PVC fitting (and valve) head loss calculations so that I know where I can optimize my circuit best?

 

[JasonLion]

Try out this chart for basic information. Finding out the same information for more complex fittings is more difficult.

 

[mas985]

I'd like to remove any unnecessary check valves (or use 2-1/2" inlets instead of 2" inlets) so as to improve my circulation flow rate. (I've already removed a few unnecessary 90's and the pool heater with dramatic results!)

However, I've heard that check valves can cause a significant head loss on any system (I have the Jandy no-lube type). Is this true? Where can I find a place which lists typical PVC fitting (and valve) head loss calculations so that I know where I can optimize my circuit best?

Swing check valves are not as bad as the spring check variety so I think you have the right kind.

The biggest bang for your buck is to upsize the pipe. Pipe diameter has much bigger effect than removing fittings.

However, given that you have a 2 speed pump, why all the concern about head loss? On low speed, any change will have a very minor effect.

 

[mgianzero]

I'd like to remove any unnecessary check valves (or use 2-1/2" inlets instead of 2" inlets) so as to improve my circulation flow rate. (I've already removed a few unnecessary 90's and the pool heater with dramatic results!)

However, I've heard that check valves can cause a significant head loss on any system (I have the Jandy no-lube type). Is this true? Where can I find a place which lists typical PVC fitting (and valve) head loss calculations so that I know where I can optimize my circuit best?

Swing check valves are not as bad as the spring check variety so I think you have the right kind.

The biggest bang for your buck is to upsize the pipe. Pipe diameter has much bigger effect than removing fittings.

However, given that you have a 2 speed pump, why all the concern about head loss? On low speed, any change will have a very minor effect.

What exactly do you mean by swing check valves? The only "check valves" that I know about use a spring type flapper. The "swing valves" I think you are referring to are 2 or 3 port standard valves. Or is there something else out there I don't know about?

According to another source, typical check valves cause quite a bit of resistance. According to another source I found (on moneysaverpumps.com) a check valve can cause an equivalent pipe length head loss around 13.4 ft (for 1-1/2" pipe) which is more than two 90's in series. I don't know what it is for a 2" line and this is the reason I asked if anyone had a chart that showed this.

Also, for a good size pool (mine has 24,000 gallons with a shared 600 gallon spa, 3 main drains and 2 skimmers and 2 spa drains and a pad run of about 40-50 ft each way) it is best to minimize all head losses by minimizing 90's and check valves, even at low flows. I removed my backwash valve (the slide valve type has effectively 4 elbows in it), and around 6 90's and replaced the rest with 45's and I was able to increase my low-flow rate from <40 GPM to over 50GPM! This made a significant difference in my eyes since I was not only able to reduce my circulation pump time, but also allowed me to keep my suction vacuum running full time by closing one skimmer and 2 main drains at low speed.

 

[mgianzero]

Try out this chart for basic information. Finding out the same information for more complex fittings is more difficult.

Yes, I've seen this chart before. But it does not include check valves, but only gate valves. I am not sure if we consider standard pool 2 and 3 way port valves as true "gate valves" since they are really the swinging type and not the sliding type which is what a gate valve is. Agree?

I find it funny that there is no reliable place that lists head loss for various swimming pool fittings such as their check valves, 2 and 3 way port valves, backwash valves, etc. This would be helpful to me in designing a most effective pool system if I were a pool builder. Am I asking for too much from the pool construction world to have this?

 

[JasonLion]

There are two completely different kinds of check valves made. One kind, for example the Jandy check valves, use a "flapper", a panel that is mounted on a hinge at one edge, to block the pipe. See here. They need to be installed in the correct orientation to work correctly. The other kind uses a large spring that pushes a round plug up against the water flow. See here.

The spring check valves have a much higher flow resistance than the flap check valves. On the other hand they are less expensive and don't care about their orientation.

 

[mgianzero]

There are two completely different kinds of check valves made. One kind, for example the Jandy check valves, use a "flapper", a panel that is mounted on a hinge at one edge, to block the pipe. See here. They need to be installed in the correct orientation to work correctly. The other kind uses a large spring that pushes a round plug up against the water flow. See here.

The spring check valves have a much higher flow resistance than the flap check valves. On the other hand they are less expensive and don't care about their orientation.

Okay. I understand now. I was confused by calling them "spring" check valves since even the Jandy flapper check valves have springs in them.

Thanks.
Marc

 

[mas985]

Also, for a good size pool (mine has 24,000 gallons with a shared 600 gallon spa, 3 main drains and 2 skimmers and 2 spa drains and a pad run of about 40-50 ft each way) it is best to minimize all head losses by minimizing 90's and check valves, even at low flows. I removed my backwash valve (the slide valve type has effectively 4 elbows in it), and around 6 90's and replaced the rest with 45's and I was able to increase my low-flow rate from <40 GPM to over 50GPM! This made a significant difference in my eyes since I was not only able to reduce my circulation pump time, but also allowed me to keep my suction vacuum running full time by closing one skimmer and 2 main drains at low speed.

My guess is that most of the gain that you are seeing came from the removal of the backwash valve and the removal of the 90s had minimal impact. Backwash valves have quite a bit of head loss, more than number of bends would indicate.

Just to keep things in perspective, replacing 6 90s with 12 45s doesn't buy you very much. At 40 GPM, the head loss difference is only about 0.07 ft of head and in some tables the head loss is identical. Even if you were clever and able to replace 6 90s with 6 45s, the head loss difference at 40 GPM is only 0.4 ft. I know that every little bit helps but given that total head loss is probably in the range of 10-15 ft at low speed, sometimes it just isn’t worth it.

As for the head loss of check valves, I don't know of any manufacture who publishes that data or even if they did, I wouldn’t trust it. In fact, the equivalent lengths of fittings shown on various web sites are not all that consistent so I think they depend quite a bit upon the assumptions used in the models.

The standard flapper type check valve that Jason showed in his post has the lower head loss of the two and the one that I would go with. If you need it, you need it, so head loss is really immaterial.

Again, the biggest gain is in pipe diameter. The head loss difference for 6 90s at 2" vs 2.5" is 0.5 ft. So if I were to redesign plumbing for lower head loss, I would first focus on pipe diameter.

 

[mgianzero]

Okay. Is there much difference b/w the different backwash valves out there or do they all seem to have a significant head loss? I removed the slide type valve (Jandy brand).

The problem with upgrading to 2-1/2" pipe is that some fittings only go as large as 2" on my system (the SWG, the filter unions, the heater unions), so I still have a few bottlenecks there. But since friction over the rest of the circuit can up upgraded to 2-1/2", perhaps it may be worth it? Agree?

 

[mas985]

Okay. Is there much difference b/w the different backwash valves out there or do they all seem to have a significant head loss? I removed the slide type valve (Jandy brand).

I have no idea. I'm just going by what little data there is and how those things are designed. You might talk to a technician at the supplier to see if they have any data but I doubt it. Again, if you need, you need it.

The problem with upgrading to 2-1/2" pipe is that some fittings only go as large as 2" on my system (the SWG, the filter unions, the heater unions), so I still have a few bottlenecks there. But since friction over the rest of the circuit can up upgraded to 2-1/2", perhaps it may be worth it? Agree?

Yes, even if you need to step down to 2" right at the equipment, it still might be worth it but it depends. The gain may not be that much since it depends on the total pipe changed and the total fittings changed compared to the parts that are not changed. You would be surprised at the head loss in the filter and heater. Those you can't change. Also with 50' runs, the head loss there is likely to dominate so changing the pad plumbing may not help very much as I showed before (0.5 ft out of 15ft). Changing all the plumbing definitely would but costly and not really realistic.

 

[mgianzero]

According to what's been said so far, the pipe diameter has the largest effect on head loss, especially for a larger pool and longer pad runs. Next in line would be the filter, heater and backwash valves to have the highest head losses in a typical pool circulation circuit, correct? The check valves, then, would make little contribution to head loss in this scenario.

So how does the new Pentair Quad DE filter compare to the standard DE filters in terms of head loss? Or would it only be beneficial to replace a standard DE filter with the Quad DE if one were to eliminate the backwash valve since these Quad DE filters are easier to take apart and clean? This would then improve water flow rates due to the removal of a backwash valve and not be due to the newer "higher flow" filter. Does this logic seem right?

 

[JasonLion]

A larger filter will have a lower head loss. Removing the backwash valve will also lower the head loss. In most cases the removal of the backwash valve will have a larger effect, but if you were starting from a very small filter and going to a very large filter that could also be significant.

 

[JasonLion]

This topic has gotten me thinking about the initiative in California to improve swimming pool plumbing efficiency. They did a study examining changes like replacing all the 90 degree elbows with sweep 90s. They concluded that although the savings from replacing even several elbows was quite small, the overall reduction in energy usage throughout California, combined with the difficulties in building more power plants, made it a worthwhile project.

They specifically reject the argument that a one percent improvement isn't worth making. Even though they failed to explore which of many possible improvements are the most cost effective, they did make a compelling argument that even small improvements can have a big impact at the regional level.

Most new pools are surprisingly inefficient. Builders use large single speed pumps way too often. Some amazingly large gains in efficiency are possible with simple steps, like changing the pump to an energy efficient pump, and using larger pipe sizes. None the less, the smaller improvements possible from using sweep 90s and other similar tricks should not be completely ignored.

It is surprisingly difficult to get good information about just what to do to build energy efficient swimming pool plumbing. Information like the head loss through different main valves or different heaters is essentially impossible to get. Every now and then you see a head loss curve for a filter, but that is quite rare.

 

[mgianzero]

Yes. That is my point exactly! There needs to be a concerted effort by all (pool builders and pool owners) to make our pool equipment more green. Not only in terms of cost savings, but also in terms of time savings regarding maintenance, etc.

I used to have a pool service man for years until I decided to renovate my pool and do the service myself. Not only have I become more of an expert with regard to pool maintenance and service, but I've learned how to save money and time along the way.

It would be nice if a place like TFP would help to put together a series of reference charts for PB's and owners to have at their disposal. It would includes helpful information such as head loss data for standard pool PVC fittings, pipe flow data, and pump efficiency data like that discovered by (mas985) in his posting: pump-efficiency-data-t10605.html?hilit=pump%20efficiency.

Particularly when it comes time for a pool owner to replace equipment. That's when the time to service our pool equipment also becomes an opportunity to upgrade it as well. We all know about going solar, wind power, rainwater and grey water systems for our homes can save money in the long run. Often times we discover that spending a little extra in the beginning can save quite a bit of money down the road.

Just last month I spend a couple of weekends revising a bit of my equipment plumbing. Revising my system allowed my 2 speed pump (which I had never really used on low speed before because of poor water flow) to run more effectively. I also eliminated my 8 year-old polaris system which was using a lot of "extra" power and replace by a more effective suction vacuum. By being more innovative by actuating some of my 3 way valves, I was able to save almost half of my monthly electric bill (we pay a lot out here in California per kW-hr) per month!