Different Types Of Inground Pools
There are many different types of inground pools and it is not always obvious which type you have. I can not count how many times I have talked extensively with a concrete pool owner, discussing details about their pool installation before they finally ask me about the pool liner. Wait a minute...if you have a concrete pool then you don't have a liner. So which is it, do you have a concrete pool or a vinyl liner pool?
The goal of this article is to help pool owners learn about the different kinds of inground pools and how these types of pools differ from one another. This information is critically important if you are going to be able to make an informed decision about how to repair or service your pool. If you have something as simple as the terminology wrong then you can inadvertently be asking the wrong questions or researching the wrong information. If you take the wrong advice with your pool this can end up costing you quite a bit of lost time and money...not to mention the frustration.
While it is true that the swimming pool industry has three main types of inground pool styles, there are also a few in-between, or hybrid styles of pools which blur the lines between the original three types: concrete, vinyl liner and fiberglass. It is not always to simple to tell what you have, and if you are a pool owner with limited experience with pools it can be all to easy to assume you have one type, when in fact you are using the wrong terminology.
Different Types Of Concrete Pools
One of the most often confused styles of inground pools are concrete pools. The first thing that will be confusing to pool owners and potential pool owners is the fact that there are more than one kind of concrete pools. Terms like "cast pools", "gunite pools" and "shotcrete pools" are all used to describe concrete pools. While there is a technical difference between gunite, shotcrete and cast pools, most often these terms are used incorrectly. At the end of the day you can argue whether a shotcrete pool or a gunite pool is better, but for as much as the average pool owner should be concerned...you have a concrete pool.
Gunite Pools - A gunite pool is an inground concrete swimming pool. Gunite refers to a concrete pumping process where dry mixed concrete is pumped through lines and mixed with water at a spray nozzle. This mix is then sprayed into place forming the base pool structure.
Shotcrete Pools - A shotcrete pool is an inground concrete swimming pool. Shotcrete is similar to gunite except that the concrete is pre-mixed and pumped through the lines wet instead of dry. It is sprayed in place just like gunite otherwise.
Cast Pools - A cast pool is an inground concrete swimming pool. Casting refers to concrete which is placed via forming and pouring as opposed to shooting and hand carving like with shotcrete or gunite. Cast pools have both backside concrete forms as well as front side concrete forms, where the sprayed pools would only have a back side form and the interior of the pool shape is carved out and trowled by hand.
* For technical accuracy, shotcrete is the correct name for the process of pumping concrete and you would have wet pumped shotcrete or dry pumped shotcrete. Gunite is no longer used to describe dry pumped concrete in any industry other than swimming pool construction
You might have noticed already what all of these pools have in common...they are all made from concrete. Technical discussion aside about the different qualities of pools when comparing cast versus gunite versus shotcrete, all of these examples describe something which should be called a concrete pool. It is essentially irrelevant whether the concrete was pumped wet or dry when your pool was built, so being a shotcrete pool versus a gunite pool holds little to no value. Even if we are only talking about terminology it is important to be technically accurate. If you have a question that relates to gunite pools, you should not look for gunite pool answers - you should look for concrete pool answers first. You want an answer about a concrete pool problem. It does not matter how the concrete got there...just so long as we are talking about a pool that has the entire shell made from a concrete substance. Almost any answers to problems that apply to shotcrete pools will also apply to gunite pools, or any other name for a pool which is entirely comprised of concrete materials. Look at it like this:
Would you call your pool a "wheelbarrow and shovel pool?" What if wheelbarrows and shovels were exclusively used to build the pool? Does that matter? No, it does not. The only thing that matters is that the pool is made from concrete and not how that concrete was turned into the shape of a swimming pool.
An important note on concrete used for inground pool construction is that all pool types incorporate concrete into the building process, including vinyl liner and fiberglass pools. It is only when your pool is entirely comprised of concrete materials, shell structure and all, that it is a concrete pool. A common mistake, for example, is for vinyl liner pool owners to see concrete on the floor of their pool and mistakenly refer to this as a concrete pool. Yes concrete can be an integral part to vinyl liner pools, but this does not mean that you have a concrete pool. If you are at all uncertain about what kind of inground pool that you have then look at two things:
The Pool Structure - The pool structure is the walls and floor of the pool. A concrete pool has the entire shell, walls and floor, made from thick concrete which is reinforced by an extensive grid of structural steel inside of the concrete.
The Pool Interior Surface - The interior surface of a concrete pool will be some form of concrete. This can be called pool plaster, marbelite, marcite, pebble finish or many other names. There are some occasions where an entire pool is made from concrete, but there is a vinyl liner on the interior surface of the pool. In this event the interior surface being a vinyl liner trumps the fact that the pool shell is entirely constructed from concrete. Pools are not built this way any longer due to the costs of concrete, but there are many older concrete pools which have been hastily converted to vinyl liner pools in an attempt to avoid expensive concrete pool repair bills.
What if you have a concrete pool, but it has a layer of paint or membrane inside on the interior surface? You would need to determine if the interior surface is painted, membraned, fiberglassed or perhaps has a vinyl liner. The liner is easiest to spot, since it requires a coping track to hang from at the top of the wall. Paint is also easy to tell, however some of the thicker paints might resemble a membrane based on look and feel. Fiberglass interior surfaces on concrete pools are hard to the touch, unlike membranes and liners which give slightly to the touch. This is where pool owners can get confused. If you have a concrete pool that is coated with a fiberglass surface, do you have a concrete pool or a fiberglass pool? The answer is that if the shell is made from concrete, then you have a concrete pool. If the interior surface is not concrete, like for example fiberglass, then you have a concrete pool fitted with a fiberglass interior surface. Or a concrete pool with a painted interior surface, or a concrete pool with a membrane interior surface. If you are not able to accurately describe what you have when seeking assistance, then you are very likely to not receive the help that you need.
Different Types Of Vinyl Liner Pools
A vinyl liner pool is probably the easiest type of pool for a pool owner to identify. If you have a vinyl liner hanging from a coping track that covers the entire interior surface of your pool then you have a vinyl liner pool. The only exception to this would be, as with the example provided above, a concrete pool that has been retrofitted with a coping track and vinyl liner to inexpensively deal with a leaking concrete pool structure. Still, this would now be described as a vinyl liner pool since it is the vinyl liner providing the waterproof layer in the pool however you would always need to qualify this by saying that you have a concrete pool with a vinyl liner installed.
Steel Wall Vinyl Pool Kits - One of the most common ways to build an inground vinyl pool is with a galvanized steel wall panel kit. The wall panels are set and cemented in place, the floor formed from either sand, grout (mortar) or vermiculite concrete, and a vinyl liner hung from a coping retainer track which is mounted at the top of the wall.
Polymer Wall Vinyl Pool Kits - While galvanized steel can resist corrosion, there are still many examples of galvanized walls rusting over time. This is usually a result of long term pool leaks where chlorinated water is allowed to access the galvanized steel directly, which the wall is not intended to endure. Polymer walls are a slightly more expensive pool wall option for vinyl pools which completely eliminates any possibility of wall rust.
Concrete / Block Wall Vinyl Pool Kits - An older style of vinyl liner pool construction was to build cinder block walls instead of ordering a vinyl pool kit. While this is still done by some builders in some areas, the vast majority of vinyl pools built today use either steel wall or polymer wall kits.
In addition to the multiple wall types there are also multiple interior surface membrane types on the market. There are some interior surface options for pools which appear to be able to be used as an alternative to vinyl liners. These would typically be spray on or paint on waterproof membranes of some kind. Sometimes fiberglass interior surfaces are applied in place of vinyl liners. This is not a process that I endorse for vinyl liner pool owners. Any time you do something "uncommon" to your pool you risk the potential that it does not work the way you had hoped. Something that pool owners tend to not think of is how your pool will impact the sale of your house one day in the future. If you are the only person within 1000 miles of your house that has a rubberized PVC membrane liner in your pool then this can deter people from buying your home. There are a lot of really good reasons to stick with the status quo when it comes to how you fix or maintain your pool. I recently encountered a pool like this:
This pool owner needed a vinyl liner replaced in their pool. They researched a less expensive alternative to replacing the liner and decided to paint the interior of their vinyl liner pool. They removed the liner and all of the flanges in the pool, sealed the floor and wall joints with a sealer, and painted the pool with epoxy paint intended for painting concrete pools. They even went as far as painting a killer whale mural onto the floor. The pool actually looks great, if it held any water, which it does not.
This person confused two different interior surface processes which are not compatible. If this person had a concrete pool and went through all of these steps, sealing cracks and painting with epoxy paint, then their pool would likely be fine. Unfortunately filling leak points in a vinyl pool shell is simply not possible. Attempting to create a waterproof interior surface in a steel wall, grout floor vinyl pool using silicone and epoxy pool paint was simply never going to work. This has resulted in quite a bit of wasted time, money and effort for the pool owner, and they are still right where they were before...they need a new liner.
The lesson to be learned from this is twofold. Firstly, you need to be careful to understand what type of swimming pool you have, as well as the differences between different kinds of swimming pools. This is especially true if you elect to not hire an industry professional to perform maintenance on the pool for you. I can totally understand the line of thinking that this pool owner was using, but unfortunately they were headed down a path with only one possible conclusion. This is the second point, in that you should specifically avoid trying to change from one type of pool to another. In this case, the pool owner attempted to change from a vinyl liner pool to something else, anything else really, and this is a bad idea. You open yourself to a world of potential problems when attempting to skirt the traditionally respected technical processes for swimming pool construction.
Converting A Pool To A Different Style
It is seldom a good idea with a swimming pool to attempt to change from one design to another. If you have a vinyl pool then you should not attempt to change it into anything other than a vinyl pool. The same goes for concrete pools in that you should not change a concrete pool into a vinyl pool and you should not (can not) change a vinyl pool into a concrete pool. Actually, that is not true. You can do anything...but you need to understand what you are getting into. For example, take a look at this article I wrote about just what is involved with actually converting a vinyl pool to a concrete pool. At best converting your pool to a different kind of pool is an expensive proposition. At worst it can be a total disaster and a complete waste of money and resources.
A concrete pool is a much more expensive and high quality pool than a vinyl liner pool. So why would you ever want to put a vinyl liner into a concrete pool? The reason is simply because you are having problems with your concrete pool and somebody told you they could just put a liner in the pool instead. Just because someone says that they can do something does not mean it is a good idea. A vinyl liner is often treated like a band-aid for structural failures in concrete pools when in reality, at least in most cases, the pool can be restored to a fully functioning concrete pool once again. Most of the time this all comes down to dollars and cents. Concrete pools can be expensive, and most especially with older concrete pools which have not been maintained very well over the years. Only in the most extreme of cases would I ever encourage someone to consider hanging a liner in a concrete pool.
Often pool owners will ask about moving in the other direction and converting a vinyl pool to a concrete pool. This is a common enough question that I wrote an entire article about how to convert a vinyl pool to a concrete pool. Basically, it is as much work as building an entire concrete pool plus the amount of work required to remove a vinyl liner pool. There is essentially no cost savings on building a concrete pool so you would have to want to convert to a concrete pool pretty badly. The only time I would consider this as a viable plan would be during major property renovations where the entire property is being developed into a high end piece of real estate. High end real estate tends to be dominated by the concrete pool market and getting maximum market value for a developed property can sometimes require having the status of having a concrete pool.
Fiberglass & Hybrid Inground Pools
In addition to vinyl liner and concrete pools there are also fiberglass pools. Fiberglass pools are any pool where the entire shell structure of the pool is made from fiberglass. This is not to be confused with a concrete pool that has been refinished with a fiberglass interior surface instead of tile or plaster or another material. Unlike with a vinyl pool where the interior surface trumps the shell construction, fiberglass is not the same. If a concrete pool has a fiberglass interior surface this does not make it a fiberglass pool...it makes it a concrete pool with a fiberglass interior surface. There are however some times where the lines between concrete, vinyl liner and fiberglass do become blurred. While not common when compared to traditional concrete, vinyl liner or fiberglass pools, there are just enough hybrid pools on the market to muddy the waters for pool owners and confuse people as to what kind of pool they have.
I dealt with a pool owner with back and forth communication extensively before I discovered that her "concrete pool" was actually a steel walled, concrete floor swimming pool hybrid. This hybrid pool style has never been very common, however there are a few notable builders of this style of pool which have created regionally dense pockets of areas where this type of pool is more popular.
Hybrid pools use wall panel segments just like a vinyl liner pool. To the untrained eye these types of pools probably look very similar however they are not built in the same way. A vinyl liner pool kit was never intended to be waterproof without a vinyl liner protecting the interior surface. A hybrid style pool is intended to be waterproof but this requires a different construction process including how you install the walls, the material the walls are made from (often fiberglass), and how thick the pool floor is. Most vinyl liner pools have a concrete floor around two inches thick. A hybrid pool will have a concrete floor up to eight inches thick and this has a dramatic effect on how well the floor resists cracking from the weight of the water, as well as how well you will be able to waterproof the joints within the pool.
Traditional Hybrid Pool - A traditional inground hybrid pool would have fiberglass wall segments which are concreted into position and held in place by a retaining ring or concrete collar at both the top and the bottom of the wall panel. The floor would be structurally thick concrete and the interior surface of the pool is painted. The water resistance of this pool is provided by the tight fitting wall sections as well as every seam in the pool wall and floor being filled with a flexible urethane sealant. Over this a high build pool paint is used, concrete pool paint on the floor sections and fiberglass pool paint on the wall sections. When done effectively this pool design represents (at least once upon a time) the cheapest inground pool construction method. Price of, and restrictions using fiberglass, have made these no longer cost effective to build. In the aftermarket, these hybrid pools do not age well as they are prone to developing leaks easily. When things fail, repairs to these pools can get very expensive.
Modified Hybrid Pools - If a traditional hybrid pool was once a viable entry level inground pool kit option, but it is no longer an option, what would happen if you changed the materials the pool was built with but kept the hybrid pool design? Could a hybrid pool design make financial sense using something other than fiberglass walls? Are there any polymers or resins that would allow you to build a "high tech" hybrid pool? Actually, yes, and that company already exists. Myrtha Pools builds pools using a process that loosely looks like a traditional hybrid pool however they have replaced the (comparatively) low end fiberglass walls and pool paint with stainless steel walls and PVC membranes. These materials make a supremely high quality swimming pool that is practically bullet proof in every regard. PVC membranes that are heat treated and applied to wall segments are very versatile and durable, but they are not very inexpensive. This style of pool construction is most common in commercial facilities where they can be installed much faster than concrete pools, and with a much more durable build quality and interior surface than a vinyl liner pool.
In addition to the three main types of pools, concrete, vinyl liner and fiberglass, there are also the hybrid pools which overlap some parts of the other kinds of pools. If you are thinking this sounds confusing, and you are not exactly sure how you will be able to tell what kind of pool you have, consider that there are many home made and DIY swimming pools out there that fall into their own, unique category. The most common DIY pools typically would be cinder block wall construction that is either rendered and painted, or potentially waterproofed with a liner. There are also quite a few types of above ground and on-ground swimming pools as well. If you would like to see some of these other kinds of pool kits you can read this article about above ground pool reviews.
Polynesian Low Hung Liner Pools
In addition to the more common swimming pool styles listed above, there is another form of hybrid pool called a "low hung liner" pool, popularized by Polynesian Pools over 50 years ago. The style of this pool was dubious at best, and the design never caught mass market appeal. The design, similar to other hybrid pools, used a different wall material than floor material - in this case fiberglass walls combined with a vinyl liner floor.
To accomplish a waterproof transition point from fiberglass walls to a vinyl liner floor, while underwater, required a liner retainer that is covered by a sealant tape. The sealant tape is the weak part of this design, and any person adept with leak detection knows how easily water will escape a pool system if there are any chinks in the armor, so to speak. Relying on tape for a finished water tight seal, regardless of how excellent the tape is, seems like a poor design to me. Despite this, these low hung liner hybrid pools are out there and there is not a lot of information available to owners of these pools. The information that is available seems to indicate that the sealant tape, previously offered by 3M, is either discontinued or has changed names to a new product. The closest likely product that I was able to find from 3M is their "extreme sealing tape" line which has a 4412N 80 mil tape as well as a 40 mil 4411N version. I can find no information to support that this product will work underwater in a chlorinated environment, however I was able to find information from 3M that indicates this tape can withstand high pressure washing without peeling at the edges, and has built in UV protection.
As low hung liners pools age they become harder to work on or recondition. Many of these low hung liner pool will end up being converted to full vinyl liner pools however this is not always an easy process. Over time the fiberglass walls tend to become brittle, and cracks can develop which can be a problem to resolve. The thin and relatively weak wall design also does not accept hardware very well so mounting a traditional vinyl liner coping track can prove challenging as well.
For most low hung liner pools eventually the seam between the vinyl floor and the fiberglass walls will be unable to be sealed, and leaking becomes a constant issue. It can also be challenging for owners of these pools to find people to replace the liner when it comes time as there is no easy solution - either the pool needs to be converted to a full liner pool, or the installer needs to try to work with the low hung liner design. In either case this will take much longer than simply installing a coping and liner on a vinyl pool, and this cost gets passed along to the pool owner.
If you are a pool owner or a swimming pool technician and you think you have a unique swimming pool design style that is not listed on this page, please contact Steve to discuss what you have. It would be very helpful if you have some pictures of the pool also to help determine exactly what kind of pool construction you have.
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