Underground Plant Room advice needed

[David00]

I'm having a small 8m x 4m, 1.4m deep concrete swimming pool built in Greece. It's a dry climate, and many pools use an underground plant room to house the pump. My builder has proposed building this alongside the pool, so that a part of the pool wall forms one side of the plant room, and he builds three other walls to create a 3m x 1.5m, 1.6m deep plant room with drainage. It has a concrete floor and roof and a sealed access hatch.

I have simple question. Are there any disadvantages of doing it this way? I can understand the advantages, he needs a little less concrete, pipe runs will be short, etc. My main concern is around noise being generated in what is effectively a concrete box, and resonating through to the pool itself.

Can anyone share their experience in this area? I'm not concerned about whether the pump room is the right size, or the right depth, or anything like that. Just whether it should be attached to the pool wall, or situated perhaps 2m away with some earth between.

What causes noise in a pool, under and on the water? Is it noise from the pump transmitted through concrete, or is it cavitation or other noise in the water flowing through the pipes into the pool? Are there specific noise issues or causes to be aware of? I'm not in Greece, and can't look at any other pools to get a sense of the noise created.

Thanks,
David.

[Teapot]

David you should be fine with the plant room provided it is large enough to hold the equipment and for a normal sized person to be able to service it.
You are absolutely correct about the sound issue, sound travel's 4 times easier through water than air. The noise through the lid can be dampened down using the same acoustic foam panels as used on expensive motor yachts.
The noise through the plumbing however is not so easy, I would recommend a variable speed pump and the services of the best pool technician you can find to engineer an Eco pool installation. This work is likely to be beyond the average pool builder.
My pool is a similar size to yours and I run mine on 90% less electricity than a standard setup and this only produces around 29db of noise. This is with proper water flow rates, I don't know how much electricity costs in Greece.

The noise is mainly from the pump, it should not be from cavitation ever as that will damage the pump.

[Teapot]

David take a look at this thread it may help a little. If you need an idea of relative db then download a sound meter app to your smart phone and take some measurements.
viewtopic.php?f=35&t=61&p=41571#p41571

[Teapot]

Will we ever hear from David00 again?

[Denniswiseman]

Will we ever hear from David00 again?

I find it very strange that people ask for assistance but never respond
You never can tell some people are genuinely grateful for the help they receive, where as others never bother to reply with any comment like "Thanks for the effort" or "That didn't work"
I take comfort from the people that we have helped, have a better understanding of there pools and chemistry and may educate others

[Teapot]

Maybe it's an ugly modern trend Dennis? after all you don't have to thank Google.
Personally I just find it rude. I do make a list on various forum of those that only appear when they have a problem, never say thank you etc.
As you say keep positive about the ones we have helped.

[David00]

Hi Teapot,

Thank you for your advice from over 2 years ago. I apologise sincerely for not replying earlier, I've only just seen it. I posted a similar question on a few forums at the time, and guess that any notifications of replies from poolhelpforum went into my junk mailbox.

Your advice in retrospect was spot on. I actually went with a German pump system from Lorentz, a variable speed 3-phase DC motor powered directly from a PV solar array - no inverter as such. My only isssue with it is low suction in winter when trying to clean the pool.

I do have a problem with damp/condensation in the pool room in winter when ground water manages to find its way through the concrete - something I'm hoping to fix shortly.

All the best!
David.

[Teapot]

Hi David, its been a while since I last visited. Ah the Lorentz pump, any idea of flow rate? A picture of your setup? I have a variable speed pump, not a Lorentz and have no problem with vacuuming when I ramp it up to full speed.

[David00]

Hi Teapot,

Thanks for your note. The Lorentz system is good - but possibly more suited to pumping well water . The pump noise close-up ranges from a low 500hz up to over 2khz as sunlight levels fluctuate, it sounds like a racing car. But outside the plant room it's fine. It still turns the pump when sun is hitting the PV panels at 80 degrees off centre, albeit slowly. This is testament to the overall pump system design, and very efficient MPPT tracking - a great bit of kit. However in the winter with low light levels, while the pump still does it's job there often isn't enough suction for cleaning purposes.

The controller runs the pump at a maximum speed of 2385 rpm, this is achieved with any DC input above 55V (12A limit) from the PV array. The pump itself uses a BLDC motor, the VEC (electronically commutated) is about 46V with 48V DC input, which provides 494W of motor power = 2245 rpm. To give you an idea of how this affects the flow, at 8M head 2245 rpm (494W) = 10,200l/h and 2385 rpm (638W) = 12,500l/h. I'm just quoting stats.

Some photos below from when I was fitting the control systems:
- The Controller photo shows the Lorentz control box (blue) with 3x 24v 270w (200w nominal...) panels connected in series as the power source. There's a 4 core cable to the pump (the 3 DC phases plus neutral). It's nicely engineered inside the controller. The rest of the IP65 enclosures are for fusing/lightning supressors and control purposes (timers, contactors, etc).
- The Pump #1 photo shows one skimmer & suction inlet, and drain down, leading into the pump, and (unused) heating circuit.
- The Pump #2 photo shows the pump going into a sand filter, and the ubiquitous "Octopus" control valve. There's also (just out of shot) a 24v DC Salt Water Chlorinator from Chinese company LA Swim (model EC-16) - For various reasons I've yet to trial this properly, but know it's in widespread use outside Europe. The battery and EPever charge controller on the floor currently provides 24v DC from a 4th 24v PV panel.

Am planning to re-pupose that 4th panel with a boost solar charge controller to charge a small capacity 48v battery - and have a switch that can be used to run the pump from the battery in the winter for approx 20 mins while still leaving it 50% charged, so that the pool can be cleaned properly. Will add a 24v buck converter to the battery to get 24v for the chlorinator and lights. In case you were wondering why I don't use grid power - I'm not connected to it.

All the best,
David.

[Teapot]

Hi David, thanks for the photos. Yes I am aware of the Lorentz pump noise, by contrast my pump a variable speed pump on filtration at around 1800 rpm produces 29dB at 2 metres.
I can easily vacuum at less than 2800 rpm because I get a high flow rate due to low friction. What is the diameter of your filter, it looks about 500mm? Also I got rid of the multiport valve as those things are diabolical for creating friction and severely reducing flow.

[David00]

Hi Teapot,

Your pump sounds interesting, can you share any details pls?

Yes, my sand filter is around 500mm diameter. I'm not there at present so can't check exact dimenstions.

I know what you mean about how the multiport valve constrains flow, I dismantled it a few months ago to check it was clear. But it's (relatively) idiot proof, and I rely on someone else to service the pool when I'm not there. Did you replace it with a number of discrete full-bore valves, or some other solution?

[Teapot]

Hi David, I use a range of pumps depending on the job at hand but I am refering to the blue Eco pump in this case.
The possibly 500mm is a little on the small size IMO, I use a 610mm but would consider 2x 500mm to increase flow and reduce head.
I have used a range of setups when experimenting from a bypass setup on a multiport so filtration was directly into the filter missing the multiport completely until two slide gate valves were closed at which point the multiport becomes a multiport once again. Useful for operators who are easily confused. Idiot proof! everybody knows every greek man was born a pool expert Hahaha. I have also used the Pentair fullflo XF and Pentair/jandy slide valves, The Pentair FullFlow is fragile and bits snap all the time! The Jandy neverlube 8034 is my current one as I intend to automate and that can take actuators.