Equipment pad plumbing configuration for addition of spa to pool

[Quartzo]

Long post, but my main questions are numbered 1-4 below. I am renovating my pool which originally had an attached spa that has been filled in since I bought the house. We have already demoed, cleaned out the spa, and found that it is recoverable so we will be recommissioning it. My current setup before the reno is in my signature. Currently my only automation is from the Pentair home app controlling the pump as well as the I/O relay control board on the pump to turn the salt cell on/off (but I leave it on all the time when the water is warm enough and shut it down completely in the winter, so there's not much need for this). With the spa being added, I will be adding automation for the valve control and heater. I am doing the automation myself so I can do things a little different than the out of the box solutions. For example I can control 3-way valves to any arbitrary position. I put a summary below of what I can and can not do with automation for the equipment that I have and will have. I have plenty of experience automating things like this, so this is not the part I need help with. My question is what the plumbing configuration at the pool pad should look like to best take advantage of automation with my equipment? We are redoing most of the plumbing around the entire pool and spa, so pretty much any option is on the table. We are also upgrading the underground plumbing from 1.5" to 2". I put an image of a configuration similar to what I will have below, for reference.

How I want to use my pool:

I currently run the pump 24/7 all year long (no winterization) and will continue to do so with the default setting being suction from pool and return to pool at a low flow setting (enough to run the salt cell). Even in spillover mode, I want the low (or high) flow to the pool return, not the traditional spillover automation mode that returns only to the spa. So to summarize I want the following settings available:

• "Pool" setting with suction and return to pool only. Optional heating at lower temperature set point. Usually at low flow, but will increase flow 1/2 times per day.
• "Spa" setting with suction and return to spa only. Heating at higher temperature set point. Flow set at optimal rate for heater.
• "Spillover" setting with suction from pool and return to pool and spa (not just spa), with adjustable amount going to spa. I will be able to adjust the pump speed, but keep the spillover rate where I want it with the remainder going to the pool.

Here are my questions:

1. I have two skimmers, but they are currently tied together prior to the equipment pad. I've never noticed any issues with the flow distribution between the two or felt a need to adjust it, is there any reason I should take this opportunity to split the skimmers with a 3-way valve, or is it fine to leave it as-is? For example, would I get more efficient flow with two separate lines all the way from the equipment pad? Does upgrading to 2" affect this decision?
2. What is the advantage of the spa make-up setup in the image, compared to just setting the pool/spa return valve to allow some flow to the spa? Is it just the convenience of keeping that valve at a fixed setting and then being able to throw the pool/spa return valve 180 degrees to change modes without fiddling with it? Given that I will be able to automate the valve to go to an arbitrary position, and will be able to adjust the position from an app or send it to a pre-set position, it makes sense to me to just use the 3-way and not the spa make-up line. Am I missing anything? I don't really want to rely on the traditional automation solution using suction from the pool only and return to the spa only with lower pump speed, but I will be able to run it that way as well.
3. Where do I need check valves? The spa is about 1 foot above the pool and the equipment pad is about 2" above the water level for the spa, as best as I can tell.
4. And the one I am least certain about - where should the salt cell be placed? I'm a little bummed that I can't adjust the output remotely. I can probably tie into the buttons on the salt system and add automation, but I won't be doing that for now. I'm worried it will over chlorinate the spa in spa mode if I leave it on. Should I put it on the pool return only? Or should I put it on the combined return (outlet of the heater) so that it chlorinated water will flow to the spa in spillover mode (but only a fraction of the total chlorine output, since I can allow most of the flow to go to the pool)? Would this be too much chlorine to the spa? Then I can either turn it off in spa only mode via automation, or by placing the flow switch on the pool return only. Is there an issue with not having chlorination in the spa in spa mode? If I start out with good chlorine levels, then in the time that I heat the spa, then use it, then switch to spillover mode to circulate it (let's say 24 hours? I don't know, I haven't had a spa before), will I have problems with sanitation? After typing this, I think leaving the salt cell and flow switch before the return valve gives me the most flexibility for the future, but just want a sanity check here.

What my automation can do:

• Adjust 3-way valves to arbitrary positions - fully one way or the other, or any point in between.
• Turn pump on/off
• Change pump flow rate
• Turn heater on/off
• Toggle heater set point between two values (eg. pool/spa). Values are set manually at the heater. I can add the ability to adjust the set point through the automation, but don't see a need to right now
• Turn salt cell on/off

What my automation can not do:

• Adjust salt cell power level

Thanks!

 

[Jimrahbe]

Q,

Have you ever even been in a gunite spa??? I ask because they may not be what you think.. 50% of pool/spa owners never use their spas, as they don't function as well as they the owners thought they would.

Thanks,

Jim R.

 

[Quartzo]

No, my wife is pretty confident that she wants it though. I'm not sure what her expectation is either. What aspects do you think may not meet expectations?

Cost-wise, I'm talking to the pool builder again this afternoon, but it looks like it is not going to be too bad. About half the cost will be the heater itself. My wife would also love a heater for the pool, anyway. I am less enthusiastic. If it were just the pool, I'd probably go with a heat pump. It's more expensive, I know, but we'd really only be looking at raising the temp a few degrees in spring/fall to extend the season a bit, and I don't love gas and I like the efficiency of heat pumps. Anyway, with the spa it will be gas. It's already plumbed.

Anyway, my point is that the opportunity that is presenting itself now is to add a spa on to our pool for a fraction of the cost that one would normally pay to add a spa with a new pool build. And we'd already have to pay to refill and deck it back over if we decide against it. This makes me lean more towards going through with it even if it does miss expectations somewhat, but I'm interested to hear your opinion.

 

[Jimrahbe]

Q,

Adding a spa to an existing pool would normally be $20 to 25K... Or more...

Most people 'assume' that a gunite spa will be just like standalone spa.. Unless specially made, they are not even close..

Standalone spas are constantly hot and ready to go.. With gunite spa, you have got to know when you want to use it and turn the heater on in advance.

Standalone spas have a million jets, gunite spas tend to have only a few jets and you don't get the same jet action that you do in a standalone spa..

50% of the owners never use them after the first year.. About 25% only use them once or twice a year.. The other 25% love them, mostly because they are designed better than the average gunite spa..

I am not trying to talk you out of getting what you want.. It just makes sense that you know what you are getting before forking out the cash.. See if the pool guy has one your wife can try out first.

Thanks,

Jim R.

 

[Hammond]

Yes, as he says the spa is not like a standalone hot tub, but we do still use ours. It’s nice when it is cold or cool to be able to heat the spa. On cool days you can go from the pool to the spa to warm up.

I wouldn’t get the heater with the idea of heating the pool. It’s hard to heat a pool in Dallas with a heater, just takes too long and burns too much gas.