TDH of a multiport valve

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H

heythatguy

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In The Industry
Sep 12, 2013
36
Fresno, CA
Split off of this topic. JasonLion

If you want the best flow with the least amount of TDH go with larger plumbing 3-4 inch, the TDH of a multiport valve, typically seen on sand filters if 50 ft head, and sand filters do not work well on low flow, the debris does not penetrate the media bed as far as it should and pressure will rise faster. A cartridge is a very good way to go, will also eliminate a backwash valve which can be a large amount of TDH. On your plumbing make sure to use 90 degree sweeps and not elbows, a 2" elbow on TDH is almost 9 ft head, so 90 degree sweeps or 45 degree elbows if you have to. You can find charts that will provide you with the amount of TDH for the plumbing that you plan yo use and then you can add it all up on the suction and pressure side to get to a number, then look the pump curve of the pump you plan on buying, then purchase accoringly. You ought to look at a vs motor or a 2 speed motor, you will like the electricity savings.
 
Re: Pump sizing help for new inground design

Head loss is dependent on flow rate so posting head loss numbers without flow rate is completely meaningless.

Also, I am not sure where you are getting your head loss numbers but they are much too high.

For example, a multi-port 2" backwash valve will have 50' of head loss at 182 GPM which is not really realistic. For a flow rate of 80 GPM, a backwash valve will have a head loss of about 10' of head (per Pentair spec sheet). Still high but not 50'. At 20 GPM, the head loss drops to 0.6' of head.

A 2" 90 has 9' of head at 330 GPM. At 80 GPM, head loss for a single 90 is only 0.53' of head which is not much. At 20 GPM, the head loss drops to 0.033' of head.

Also, sweeps have about half the head loss as 90s but 90s only make up a small portion of the total head loss in a typical plumbing system (~1% per 90). Normally, it isn't worth the effort to go with swept 90s. It is much easier to simply upsize the pipe. But even that has diminishing returns and plumbing a pad with 3 or 4" pipe is not easy. I would stick with 2.5" pipe.

Lastly, from users experiences on this forum, sand filters work much better at lower flow rates than higher flow rates. Too much flow rate can push debris through the sand.
 
Re: Pump sizing help for new inground design

I got the numbers from Bob Seward of Hayward, at this years PIE(Pool Industry Expo) in Monterrey. Sorry that he did not specify the gpm for the friction head loss numbers.
 
Regardless of flow rate, I can tell you for certain that ball valves are temporary. As has been reported in many other pools AND my pool, you get about 2-4 years service at best from them and they "lock up".....not exactly sure why.

IMO, even though I know they are used all the time, it is pointless to install your plumbing with Ball Valves......Go ahead and bite the bullet on the Jandy-type valves....money well spent
 
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