Heaters have two regulators controlling how much water from pump enters the heat exchanger in the heater. One is pressure sensitive (controls flow into/bypass heater), the other is temperature sensitive. As water cools. more water enters heater, and as it gets hot, more water is bypassed. Both work in conjunction to adjust how much water goes through the heater and how much is bypassed. I'm sure it may vary by region, but in my area, (Texas Gulf coast) I've only seen a few heaters with manual 3-way valves to take the heater off-line altogether. (Since mid 1990's). As far as chems affecting the health of the heater, there are two main considerations. If you are on a salt system, get a heater with a cupro-nickel exchanger. Salt is inherently corrosive, and an all-copper exchanger will fail more rapidly, with added" benefit" of scaling inside the exchanger. Otherwise it's all good but you have to keep a close eye on balancing chems. The other is in the case of vinyl/fiberglass pools, be sure to keep the pH up in range as they have a tendency to run low on pH. I've seen many of these pools with the plumbing hard plumbed bypassing the heater because the heat exchanger has holes in it. This comes from one pool tech who is nothing more than the sum of my own experiences. Thirty years in, and still learning! Always looking forward to your new posts Steve!

Another greatly informative video, ty Steve

its also for the chem to not go thru the heater elements and wear it. I added a bipass. 24hours? you can leave it for a month or more

I am about to replace my old Hayward H350 10yrs old with a new Raypak Avia HD Nitek 404 and will be re-plumbing. I was considering adding a heater bypass cause I have SWG pool. I keep my water pretty balanced but the Hayward did eventually pop leak in the exchanger. My question about the bypass is if it can be done using a Hayward Goldline GVA 24v actuator, and automate the bypass when the heater is not calling for heat. I have a Hayward Proligic 8 controll system with open Aux ports. Have you ever seen a setup like this or is this a bad idea. I have yet to find a video online only a couple not so descriptive forum posts. If you have any advice for this unique setup I would appreciate it. I’m in Canada in Winnipeg so gas heat 3/4 of the season is a must. I would like to avoid having to manually turn the bypass on and off every other day. Lmk thx

What you state is pretty true as you typically are. But under the circumstances a customer had an indoor pool/dehumidification/pool heat pump the built in or added bypass (which is required) sets the flow through the CuproNickle heat exchanger to create the temperature differential which is needed by the indoor system in order to heat the pool water, dehumidify the enclosed pool room and/or assist in heating the enclosed pool room air. The heat exchanges are made of metal that is pretty much not damaged by chemicals. I have some out there still working that are over 25 years of age with the same water heat exchanger. The water flow must be set according to factory specs/application or the efficiency will be down, the compressor head pressure could be too low or too high which will effect the life of the compressor. And the dehumidifying process will also be negatively effected.

In Public pools heaters with internal bay pass are required because County Health Depts. Have a specified turnover rate. I understand heaters such as the old Laars, A O Smith and Raypak have internal bypass. It’s more of a blending process. Of course this may be a regional issue I’m more familiar with SoCal area.

I have an external bypass that I plumbed in an unliked what many people do, I actually pull the drain plug on the heater and disconnect the inlet and outlet lines. I also flush it out with a hose. Is it a pain in this a@@? Yes, but it’s cheaper than a new heater in 2-3 years or less. Screwing in a drain plug and screwing in 2 PVC lines is a snap!

Steve hi and thank you. We live on lake a wet incline so it’s problematic and expensive. Could the lake water act as walls as a way to have a swim lane or something my muddy Tenn river we love but I hope physics isn’t the problem Secondly I haven’t heard you mention the on-ground pool kit you are into? He’s 6’6 so how about 12x12x6 or some real bang for my buck ideas

Im looking at pool heaters. Had a solar heater but was removed with roof repair after hurricaine Ian. Plus roof guy noticed that solar was leaking and thats why my alum gutters were rotting. Anyway i had a bypass set by temp to go thru solar or bypass. Can i use tge same plumbing?

What's your favorite Heater for reliability? Thanks

Would an internal bypass type heater still need an external bypass for super chlorination purposes? I assume the bypass is an automatic thing and to be safe you would still build in an external because with the pump off I’d want to be safe.

Hey Steve, Would it be a good idea to parallel 2 heaters in the same system? One being heat pump. And the other a gas heater.

Is a vinyl pool good in North Carolina?

Could you please help me? I am having problems with my chloine level. The pool store recommended 9 lbs of shock(power powder plus) i did that and had the water tested 2 days later and was told i needed 9 more pounds of the same product. Free chlorine was .25 and total chorine was 2.32. What should i do?

I am currently installing Raypak heaters. The instruction manuals call for a Bypass Spring Valve if the Pump is over 2.0 HP. Since I am using 3.0 HP I am left with this conundrum. We normally would install a Ball valve and regulate the maxflow to about 50 Gal. x min. at 3000rpm to account for the Spa function. The Raypak engineer is asking me to find a spring valve with a 10lb Spring. I have not been able to find one, and the Raypak valve is almost $300.00 Do you have any advice. Kind regards.

$3000 for a heater? What year is this 2020? Lol If you close circuit the heater don't forget a pressure relief valve just in case.