Equipment pad above or below water level?

[BW]

Last year we had two PBs out to discuss a new in-ground pool, and I soon realized that I wanted to be better informed before proceeding. So please help me on my quest to learn more.

Both builders identified the same spot near our house for the equipment pad. It seemed logical because it's close to where the rooftop solar will be. However, it just occurred to me that this location is about 18" below the pool water level. What are the implications of placing the equipment below WL?

The best above WL location would add about 80' (roundtrip) to the solar run.

Thanks.

 

[zea3]

Unless the low area is prone to flooding it should be fine. Your pump won't have to work as hard to prime since you will have gravity working in your favor. Just about all above ground pools have the equipment 3 feet below water level with no ill effects. The only real difference is the in ground pumps are self priming and above ground pumps usually are not, to the best of my knowledge.

 

[JohnT]

The biggest downside is that you'll have to valve everything to keep water from draining through the equipment when you work on it.

 

[bk406]

And if sometihng ever let go, your pool water would drain. I wouldnt put the equipment below the water level if at all possible not too.

 

[JamesW]

The 80 foot round trip to the rooftop solar won't be any more work for the pump as long as the pipe is sized correctly. The critical pipe size is to the solar. The return trip is basically free since you have the water falling back down. The vacuum relief valve does not allow a vacuum, and therefore, you cannot regain any head loss from going up to the solar except what the return trip would have cost.

The spot near the house would cause some equipment noise concerns for whatever is on the other side of the wall.

How high is the roof that the solar panels will go on?
How many gpm will the solar panels require?

 

[racket]

Slightly below grade is an optimal position for a pump to be. I notice that flooded suction pumps tend to last much longer than ones that have to pull up to prime.

Since the heater won't be significantly lower you wont have to add a flow switch, but a pressure relief valve is mandatory on any heater that has a valve after it.

 

[Durk]

Both my pools (going back to 1946 before I was born) had pumps 18" - 3' below the water line. I think it's perfect. My current one (18") is gravity priming when full, but the returns gravity drain back to the pool when the water is dropped for closing. (I still blow them, but not much comes out). And being able to flow water to the open trap makes basket cleaning a snap. Turn off pump, dump basket, and then dunk it up and down in the overflowing trap. Close valve, cover, open valve, turn on pump. Back in business.

If something ever lets go, I can only lose 18" of water. Same as every year when I close. Maybe 30" if the drain plug on the filter popped out.

 

[bk406]

The biggest downside is that you'll have to valve everything to keep water from draining through the equipment when you work on it.

That was my thought. I still wouldnt put the equipment below the pool for an IG. As Zea pointed out, equipment for an ABG pool is below the water level, but the pumps usually arent self priming. I would still put the equipment for an IG right at or slightly above the water line. My opinion of course

 

[BW]

Thanks for the feedback. I hadn't thought about the possibility of a plumbing failure causing flooding, but we have good drainage so the mess wouldn't be too bad.

I did discuss pump noise with one PB, and he assured me the variable speed pump (intelliflo) would normally be running slow and wouldn't be heard in the house 5ft away. Is this reasonable, or his he just trying to avoid the extra work associated with longer plumbing runs?

 

[carolina pool]

Have to chime in with racket and Durk on below level installations being better. The system in general is more forgiving and efficient. If the water level gets a little low or the system has an air leak, the pumps can still function without losing prime or overheating. You avoid the snowballing problems of unions, seals and bearings that come with an air leak.

 

[racket]

Thanks for the feedback. I hadn't thought about the possibility of a plumbing failure causing flooding, but we have good drainage so the mess wouldn't be too bad.

That can happen on any installation.

 

[bk406]

But it wont drain the pool significantly if the equipment is at or slightly above the water line.

 

[duraleigh]

Interesting thread.

If the pump is installed below pool waterline, does anyone think it would eliminate or reduce a suction side leak?

What if you could set the equipment at different heights so that the pool water, top of the skimmer basket, top of the filter, etc. were all at an identical height? Almost surely not worth the trouble but it would seem to incorporate some advantages.

 

[Bama Rambler]

If the suction side piping were large enough then the pump couldn't create any negative head so it couldn't pull air into the system even if there were a leak. That would take an incredibly large pipe to overcome the negative head. If you think about it it would have to gravity flow the amount that the pump outputs (i.e. 60 gpm)

 

[JamesW]

If there were 100 feet (equivalent) of 2-inch PVC for the suction, then the pump would need to be about 6.4 feet below water level to gravity feed 60 gpm.

If there were 100 feet (equivalent) of 2.5-inch PVC for the suction, then the pump would need to be about 2.7 feet below water level to gravity feed 60 gpm.

If there were 100 feet (equivalent) of 3.0-inch PVC for the suction, then the pump would need to be about 11-inches below water level to gravity feed 60 gpm.

 

[Bama Rambler]

Thanks for the calculations James and just for clarification, the skimmer(s) connection(s) and/or main drain connection(s) would have to equal 3" too. And in order to take the pump strainer basket lid out of the equation the pump suction port would have to be 3" also.

 

[racket]

Thanks for the calculations James and just for clarification, the skimmer(s) connection(s) and/or main drain connection(s) would have to equal 3" too. And in order to take the pump strainer basket lid out of the equation the pump suction port would have to be 3" also.

It will alter the feet of head required to push the water, but if you have a 2" skimmer connection feeding a 3" pipe, you don't have to goto the 2" sizing. It will slightly change the results for the 3" pipe.

 

[carolina pool]

I think what racket is saying, is that the velocity will increase as it passes through the 2 inch openings adding a nominal amount of head to the everall system.

Historically all large installations such as Y's, swim clubs etc. were built with a pit for the pump about 3 feet below water level. This allowed them to use flooded suction pumps that operated a 1750 rpms with open faced impellers which produced the same flow as a self priming pump with a closed face running at 3500 rpm. Translating to a large energy savings.

 

[Durk]

This water loss issue is bogus. If there is a failure under pressure on the pressure side of the pump, it will lose water until the pump loses prime at the skimmers or until it goes dry at the main drain--no matter what level the pump is at. If there is a major fail NOT under pressure (unlikely as that is), you will only lose water until the pool and the leak equalize level. Probably 18" or so worst case. It's just a non-issue.

 

[bk406]

It's just a non-issue.

It depends on your water rates. On an 18x36 pool, 18 inches of water is around 1000 cubic feet. In a lot of massachusetts for example, water rates are easily $9-10 a CCF. For 18 inches of water, thats around $100. Not a bank breaker but an added expense. For a liner pool, 18 inches of water loss could cause some liner issues. Again, nothing that couldnt be fixed with some expense.