Dual Pool Heaters Pool Build: Plumbing, Pump and Cartridge

DiveController

New member
Dec 4, 2019
1
Texas
I am a newbie to the forum stuck in the middle of a pool build with some significant concerns regarding future circulation and heating. We have a gunnite shell in the back lot with the stub plumbing (and most of the long plumbing in place). This cannot be altered easily without very significant additional expense.
We have currently paused our pool build to ensure that we can adequately heat the pool eventually.

Our 'Pool': 58,000 gallons (4 feet, shallow end & 11 feet at the deep end)
Intended Use: Extended swim season (as one of our children is on swim team), at least March through November (possibly year round, or whatever is reasonably affordable)
Our current estimated time for one circulation (per our builder) is approximately 12.5 hours. I believe the current set up is probably sufficient to allow enough circulation to avoid any problems with stagnation, algae etc. and correct mixing of chemicals to keep the pool water essentially trouble free.

Primary Concern: Very extended time to heat the pool in colder months (it won't require any/little in midsummer where shallower pools can become too hot in TX and you're wondering if you should have installed a chiller).
The current guestimated time (from builder) is approximately 30 hours to heat the pool from (say) 60° to 80°F (latter is probably the minimum acceptable temperature for children)

Our Pool builder: underestimated the pool volume by 17,000 gallons. Unable to get specific flow calculations, dynamic head, etc., generally somewhat unhelpful, (rapport has been lost due to other issues). Most recommendations seem to be guesstimate rather than being based on calculated probabilities for the specific build.

I’ve listed off the current specification for the pool (below) as best I can with the hope that more experienced contributors to this forum may then be able to offer solutions (and a little hope) specifically for this project.

What we'd like:
A trouble free and functional pool for our intended usage (above)
To ensure that we put in place appropriate equipment/systems now before it's covered in decking and become a regret
We would like not to be completely gouged by the builder for unnecessary additions (we realize there will be additional cost for upgraded equipment but prefer that to a substandard build)

Proposed solution: (current setup is listed below)
The proposed solution would be to add a second identical 400,000 BTU Jandy JXI 400N 400k BTU heater (seems to be little difference in price for lower BTU heaters)
Heater would be placed on the deep system (circuit 2) and fed from a single surface skimmer (I have some concerns about this and wonder if both surface skimmers and the main drain from the deep end could be a common supply to both circuits with their respective returns?)
An additional 2.7 HP variable speed pump and filter cartridge would also be required on this separate circuit (see builder/Jandy comments below)

Current set up:
Gunnite in place PVC with plumbing in open trenches
Plumbing:
Drains 2.5" main drain from floor on deep end
2 surface skimmers (one at either end)

Returns (to pools)
Circuit 1:
2" return pipe with Tees feeding 6 x 1.5" surface returns (with 1 inch eyeballs)
Circuit 2:
2" PVC pipe to 2 x 1.5" floor returns at the deep end (no eyeballs to maximize flow with new heater)
On/Off valve intended to:
1) Divert heated water to superficial returns only (Off) in colder months (we'll be swimming in the top layer), or
2) Additional circulation to the two deep end floor returns (On) can be manually turned on (to provide better mixing/cooling in very hot summer months)

Current Heater: Jandy JXI 400N (400,000 BTUs, no Versaflow included on this type)
Current pump: Jandy 2.7 hp variable speed (builder initially recommend single speed which will expensive to run & be legally obsolete in TX by 2021)
Current filtration: Jandy CV 580
Chlorinator: Jandy Fusion Inground Chlorine Tablet and Nature2 Mineral System
Automation: iAqualink (4 functions max, I believe)

** Statements from the builder/ Jandy/Zodiac representative
  • Two 400,000 to BTU Jandy heaters cannot be placed in series on the same circuit as this would be extremely inefficient/inadvisable
    • The second heater must be placed in its own circuit (using the deep system, 2 x 1.5" deep floor returns only, no eyeballs)
  • The 2.7 HP Jandy variable speed pump may not be sufficient to provide flow to both heaters, one on circuit 1 (surface) and one on circuit 2 (deep system) when the additional heater is installed on the latter, (although intended to circulate both when a single heater was on the surface circuit only)
    • The second separate circuit (deep system) will therefore require its own separate additional pump
    • The second circuit will also require an additional CV340 filter cartridge (to prevent increased of any debris into the pump/heater)
  • Pump for circuit 2 (deep): variable speed pump must be used as the present piping (with only two deep returns) would be overwhelmed by a single speed pump 3450 rpm)
  • An additional chlorinator would not be required on the second circuit (sort of at my insistence) but a filter cartridge would.
  • Sufficient flow would exist in the second circuit for a 400,000 BTU heater to operate at 84% capacity (we'd be ok with 184% of present heating capacity)
 
Last edited:

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,829
Northern NJ
Welcome to TFP.

Let's get some facts into evidence.:
- 1 BTU will raise 1 lb of water 1 degree.
- 58,000 gallons is 484,000 lbs of water
- NG heaters run at around 80% efficiency so a 400,000 BTU heater will generate 320,000 btu's
- One 400K BTU heater will raise 58,000 gallons by about 2/3 degree an hour
- Two 400K BTU heaters will raise 58,000 gallons by about 1.3 degrees an hour

Do you have sufficient sized NG line to run two 400K BTU heaters plus your house's gas demands?

Raypak has commercial pool heaters with 1MM and more BTU outputs.. If you have sufficient NG service and use one properly sized heater it simplifies your plumbing.




You need to look at the design and equipment used by large public and commercial pools. What are the dimensions of the pool? Do you have plans you can share?

Chlorinator: Jandy Fusion Inground Chlorine Tablet and Nature2 Mineral System
I think we will all strongly recommend you get a properly sized salt water chlorine generator system for a pool of this size. Using tablets is not a long term strategy. It adds CYA to your pool which in a few months will make your water chemistry unmanageable. And the Nature 2 system adds unwanted metals to your pool which can eventually lead to staining. Read...
ABCs of Pool Water Chemistry


Our current estimated time for one circulation (per our builder) is approximately 12.5 hours. I believe the current set up is probably sufficient to allow enough circulation to avoid any problems with stagnation, algae etc. and correct mixing of chemicals to keep the pool water essentially trouble free.
Pool turnover is a myth. Proper sanitation is maintained by the chlorine in your pool, not by how long the pump runs. You can read Determine Pump Run Time - Trouble Free Pool for more on that.

Unable to get specific flow calculations, dynamic head, etc., generally rather unhelpful. Most recommendations seem to be guesstimate rather than being based on calculated probabilities for the specific build.
@mas985 may be able to help with that if you share sufficient design details.
 
Last edited:

swimcmp

In The Industry
Nov 8, 2011
1,072
Moberly,MO
Pentair makes the ETi 400 series heaters that are 96% thermal efficiency. We have built several 26 by 50 pools that we are able to heat with one 400k btu heaters. The chillers are not going to be able to handle cooling that volume of water. I think Pentairs chiller is only rated for a maximum volume of 40,000 gallons. Depending on what part of Texas the added heat during summer may require two chillers rather than two heaters.
 

JamesW

TFP Expert
Mar 2, 2011
16,599
You don't need 2 heaters if you're going to keep the pool heated.

Two heaters only help for the initial heatup.

I would just use 1 heater.

You should not get a tab feeder or a mineral cartridge.

A salt system would be a good choice.

You should get the full automation with the subpanel.

You don't need to worry about "turnover".

For heating, you need about 40 gpm.

Otherwise, you can run at about 30 gpm.