I would put check valves on the discharges of the multiports to prevent water backing up in the filters when one (or more) pump is off. The backwash should be shut off by the multiport when not being used so it may not be required. I'd probably put a check valve at each one so I could open the multiport if I needed to.

The salt cell(s) need to be plumbed in right before the return goes thru the wall. It should be after all the other equipment.

Whether a check valve is set on the filter or pump discharge won't make much difference but which ever side has it, the other should have a 2 way valve so it can be isolated for service. I would, as my preference, put the check on the pump discharge and the valve on the filter discharge.

If the back wash lines are tied to the same waste line, a check off each filter's waste is appropriate to prevent back flow conditions.

Still have those open questions on the pipe sizes in the equipment room to the pool and the return inlet sizes and quantity in the pool.

There still needs to be an SVRS system in the equipment room.

Scott

Can you run multiple cells in series?

The SVRS would be on the suction side before any of the pump intakes right?

Cells are not normally in series. In addition to chlorine, hydrogen can be produced.

An SVRS is on the suction side. This won't be easy either given the shared nature of the submerged suction outlets and the number of pumps.

Scott

Chill, where are you located?

As a biased contributor (heh heh heh) you should go with salt. The salt system would be installed after all your equipment and on the return line. This will most likely be done in a bypass configuration, so it should be designed into the replumbing job.

Regarding your plumbing, definately replumb. Is the equipment below your pool level? If it's below grade, the water will naturally "flood" the pumps so your suction side pipes should be sufficient for suction from all 4 pumps.

I tend to agree with Scott, your suction and discharge side plumbing appears to be very hydraulically deficient. Looking forward to more photos.

1. Most commercial pools have a single pump the average life on a commercial pump, and motor is 10 years so failure as it may happen shoudlnt be that big of a deal




If the return plumbing is too small the amperage of the pumps would decrease causing them to run cooler. The pressure will cause other issues, but motor wear is typically not one of them.

SVRS are not required, but it is my understanding that you cannot have a check valve anywhere on the system with an svrs on it.

SVRS are not required in most places.

Suction side check valves work well if you install high quality ones such as the pentair, and jandy ones. They must be spring assist swing type not ball, or plate style.

1) It's a mess, and impossible to service. If it were mine I would redo it.
2) Every state, county, city, etc has its own health codes. Most States I have dealt with require a 6 hour turnover in a pool of this type. So for the sake of having a place to start I will assume that this is how your .gov sees it

120,000/360 (minutes in a 6 hour turnover) = 333.33~ GPM

Judging by those photos the filters are pentair/pacfab TR140 filter.

They are 7.06 square feet. Most states have a maximum of 20gpm per sqft 7.06*20= 141.2 gpm per filter or 564.8GPM total would be the maximum usually I like 15gpm per SQFT so 423 GPM

So you definitely have enough filter for your 333 gpm flow rate.

Judging by the spacing on the flange bolts I am guessing its 6" on the suction and 4" on the return.

6" pipe @333 GPM = ~3.72fps which is a great number.
4" pipe @333 GPM = ~8.17fps which is above most health department standards but still will work (just inefficiently)

3) A 10hp pump is going to be WAY TO BIG! A 7.5 would fit the bill nicely but do cost significantly more than smaller pumps.

2 of the Pentair whisperflow XF should be able to do the job, but it would be hard to calculate this exactly without going over the entire system.

4) Salt works great. It isn't for every pool, but it works very well on most pools. The #1 key factor to a salt system operating properly is the attentiveness of the operator. If they are inspecting and cleaning the cells at regular intervals all should for the most part be good.

You can plumb cells in series. I have done this with many different products, but especially the Poolpilot systems that Poolsean deals with (my brand of choice).