Another Swimming Pool Build

[Mike Judd]

I think the walls in Thailand are massive overbuild like you stated . I've been looking on the internet and many swimmingpools in the western world are build using a single layer rebar at 25cm spacing ( 12mm rebar ) , with 15 to 20 cm walls .
sezze Posts: 202 Joined: Mon Aug 23, 2010 11:26 pm

Just an add on to the above, I have referred the swim pool construction details to two very qualified construction engineers, and both said exactly the same. An in ground pool in stable ground only needs to be 150m.m. thick all over with a single layer of 12m.m. Reo spaced 150 m.m. apart in the middle of the concrete. Min splice for all Reo 400m.m. (40 times dia) The wall to turn out into a 600 m.m. wide beam at the top. Pouring in two stages (Floor----Walls) with a water stop is obviously the easiest method. With the walls you either need a very accurately trimmed hole, or some sort of formwork---blockwork besides the inner formwork. All of this still depends on correct placement of the steel and the right amount of vibration when placing the higher grade concrete, especially at the bottom of the walls. Stay away from the wet soup mix that most Thais favour.
The above is how I intend to build my pool , but then it's only 7mt X 4mt X 1.5mt constant depth, so I don't see the need for any beams in the slab part unless the ground turns out spongy on excavation.

[jazzman]

You're probably right Mike, and the engineers you consulted. but some of your technical terms may not be quite as universal as you might imagine, and even had me confused for a while.

Pool engineering is not rocket science and as an art & business that generally gets handed down, like funeral parlours, through the generations, rarely needs any qualifications to back it up. The problems begin when those who think, 'Hey, there's a whacking profit on building swimming pools - I'll move to Pattaya, Phuket, Samui, Thailand and set up shop'. They set up shop alright, but then start guessing how to build pools, and many of them get it even more wrong than some of the DIYers who post on this site.

The DIYers can be forgiven for getting it wrong though - just like the guy who died because he changed his brake pads and didn't know about bleeding the hydraulics afterwards - because they almost all go back and try to re-invent the wheel, or at least the building methods, and worst of all, won't accept the solid advice when it comes from a professional for free. Serious market research has proven time and time again that the only real advice that is heeded is advice that is paid for - it's simply psychological, who wold want to give good advice for free? If it's free there has to be something wrong with it!

We tend to over-engineer here in Thailand to compensate for any invisible or not immediately recognisable lack of quality in the construction materials. Unless you're a pro and have been living, breathing, and eating cement powder and concrete for 40 years, you won't know a good mix from a bad one until it's too late, even if it does pass the slump test. Two years later you'll be slumped in your deck chair looking at the collapsed mess of tiles, concrete and twisted steel that is left of your 2 million baht swimming pool that you oh so cleverly got built for only 400.000

Yes, a real pro can build a small pool on 15cm thick walls and floor, wider rebar spacing, and thinner bar - and he will have the history and experience to prove that he hasn't had any complaints, and will still be around in 10 years time to support his 'company's' guarantee.

[MGV12]

What they never appear to do here ... in a domestic environment anyway ... is assess the ground upon which a swimming pool ... or more importantly a house is built.

There is a common saying "A house is only as good as it's foundation" and that is undeniably true. So in Thailand they tend to over-engineer the foundation just to be 'sure'. What is also undeniably true but not, it seems, taken into account at all is the ground upon which those foundations or that swimming pool are constructed. If you know what you are doing it can save on the over-engineering. If you/they don't know what you/they are doing it can lead to even a seemingly 'over-engineered' structure being inadequate.

[Mike Judd]

Jazzman and MGV12 ! You are both absolutely right with your comments on my post. It does depend first on the ground you are building on, and then the attention to detail with the actual build. I would appreciate knowing the particular terms that I used that need clarifying for our less experienced members. As far as following advice given on this subject previously by yourselves, I cannot fault it as far as if followed you shouldn't have a problem, which should be the priority in the end.
I just wish I could get over there and get started on mine. Mike.

[Mike Judd]

I thought I would post a couple of photos of a pool in Sydney at a house over looking the Pacific ocean, where I had a job. Absolutely gorgeous, but then at B 120 million it should be. The pool is similar to what I want to build at my house in Thailand, but I like the wet end instead of a skimmer box, my one would have to be a shorter drop as i wouldn't have the height.

[jazzman]

Yea, an infinity edge like that would turn any lap pool into a white-knuckle ride
That said, skimmers are now practically a thing of the past - for both reasons of technology and aesthetics. An infinity edge is infinitely (pun) more efficient than a skimmer even if there is not the hair raising view to go with it. Systems with a gutter all round provide not only the flush-to-deck water level, but a far more efficient cleaning and filtering of the surface water, plus the fact that every time someone jumps in and displaces water, another surge of it goes to the balance tank where it again gets better mixed and then sucked up together with some water from the main drain into the filter.

Filtration times used to be around 12- 14 hours per day, but with such new concepts and a few new clever filter media in the filters such as zeolite (marketed as Zelbrite™), pool filtration times are now down to as little a 5hrs in 24 (in ideal situations) and more environmentally and energy friendly. Saltwater chlorination has also got rid of the highly inefficient empirical dosing of the municipal swimming pools that used to get your eyes smarting before you even got near the over-chlorinated water. When I was a very young boy, we used to live within 300 metres of an open air council pool and we could smell the chlorine from our back yard when the wind was in the right direction.

[Mike Judd]

Just a question on the infinity edge pool like the one in my photo. What are the options with it, is a surge tank a must,and if so how big would it have to be for my pool of 42,000lts ?

[Mike Judd]

i have just had a read of the Infinity edge pool section and getting the drift of it. but would still like any critical points to a system where the drop area (pond) does the job of the surge tank. Keeping it full manually or with a valve would be necessary , but what about the outlet levels to the pump etc; Is there an ideal ? Then I can do a sketch of the whole thing.

[jazzman]

The infinity edge catchment can be a gutter. This would gravity feed to the balance tank. Several large diameter pipes (3", 4") are required because the water must return to the tank at the same rate it is being pumped into the pool from the filter.
On the other hand, the catchment can be a larger trough that can serve as the balance tank. It would need to be kept full at all times and be equipped with the float valve for topping up that would be in a normal balance tank. Recommendations for balance tank water volume vary in different reports and documents. Anything between 5 and 10% of the pool volume seems to be the norm and depends on the expected displacement by the bather load at any one time; sufficient head is required in the balance tank for the surge. Balance tanks are likely to become full to their overflow during the rainy season. This is when the greatest loss of water/chemicals will occur.

[Mike Judd]

Thanks for all that, ! Just one more question for the time being, if the trough is the balance tank , at what height does the bottom return drain to the pump have to be relative to the pump itself.As I intend to build the pump house along side the end of the pool by the Patio from the house, it will certainly be higher than the bottom of the trough. The top of the pool level with the patio is about 1mt above ground level, so maybe I might have to go back to the skimmer box type pool.?

[jazzman]

try to avoid a skimmer type design at all costs. Chances are the plastic lids will get broken sooner or later, the weirs will drop off, and the baskets will get mashed up. Once a skimmer has been set in the concrete wall you can't change it. Fewer and fewer pools are being constructed with skimmers these days and skimmers are beginning to become obsolete with spares being difficult or impossible to get

You can locate the pump wherever you like, especially below the water level, but preferably not higher than the water level of the pool, or maximum 1 meter above it. when choosing a pump, be sure to choose one that has a flow rate that will exchange the entire water volume in 6 hours of pumping plus a safety margin, and if the pump is further away from the pool than 4 metres or higher than 1 m, choose one that's 0.5 Hp more powerful.

[Roger Ramjet]

Jazzman,
Can you please explain why skimmer pools are becoming obsolete and why the plastic boxes and lids break. There will only be three people using my indoor pool, so do I need to lecture those people (including myself) or is it caused by sunlight?

[jazzman]

Skimmer designs are becoming obsolete simply due to:
1. The aesthetics of having water flush-to-deck and/or infinity edges
2. A far greater efficiency of getting most of the water to the filter rather than just the surface water in the vicinity of the skimmer.
3. The automatic topping up possibility offered by balance tank systems.

The plastics in all but the most expensive skimmers are of low quality ABS and after a few years the sunlight makes it brittle. When you need to replace a broken lid you can't get one, and a skimmer unit is impossible to change.

Cheap skimmers start at a few hundred baht, while the good professional ones of the same size/capacity cost a few thousand. The skimmers in my 25 year old pool in France are made of metal - along with all the other fixtures and fittings - long before plastics were used a lot in pool design. There are no metal skimmers available today AFAIK.

[Mike Judd]

Thanks a lot for that Info, I can really go to town with that part of the pool design now, using what artistic ideas I can come up with. That's one good thing about doing a build slowly, you have time to use or discard all the options.

[Roger Ramjet]

Jazzman,

Cheap skimmers start at a few hundred baht, while the good professional ones of the same size/capacity cost a few thousand.

If you took the cheap plastic skimmer to say an aluminum or stainless steel welding shop could one be made? It's just a box after all. Or is it?