New member advice

[f1fanatic]

Hi to you all,

Just joined the forum, so firstly... Hi!

I live in valencia, Spain and having recently bought a house with a pool I have inherited a pool pump system that drastically requires replacing and upograding. the current set is has been very poorly done with incorrect sized threaded connections (apparantly PTFE tape fixes all issues? lol) so I want to start again and do it properly. The current set up is probably approx 10 years old so nothing to salvage im afraid.

The pool is an inground pool, 10m long x 5m wide (excl steps) and is in a roman shape. I have measured the depths in 3 places and determined the volume is approx 75m3 (75,000 litres)

The issue is that the pump and filter assembly have been sited too far away and above the height of the pool. all pipes are buried under landscaped gardens and concrete, so no access and no option to relocate.

Distance from head (step end / Return pipe outlets) to pump is 30m, distance from skimmer intakes to pump is 40m.

Head (from surface of water to approx height of inlet to pump is 1.2m, with the pump above the water line)

Existing pipe work all has an exterior diameter of appeox 50mm

There is no non return valve fitted to the system.

pool has normal bottom drain, twin surface skimmers and side / hoover drain.

My maths so far.... which i need some help confirming im right!

Volume of water 75,000 litres. turnover time of 6 hours = a flow rate of 210 litres per minute / 12,500litres per hour /
m3 per hour

currently the flow through the system is very poor as i suspect the pump is worn, it takes approx 20-30 mins to prime, leaks at the joints and the filter has a leak and registers 0psi on the gauge.

My plan is to fit a non retrun valve just before the pump inlet to stop the water flowing back everytime.

My question is what size cv/hp pump and filter should i look at? it currently has a 60cm filter but i cant tell what flow or power the pump is/ I have looked at a 1.5cv pump, but it needs a 750mm filter which trebles the cost. Would a 1cv pump and a 60cm filter be sufficient given the distance, height and pipe diameters? or should i go for the 1.5cv and 750mm filter? I assume the distance and height would mean that i need to calculate in possible loses, hence why i was considering the increased power. Obviously the pump would have be self priming due to being above the water level.
(The new filter medium will be glass, not sand)

Apologies for the long first post, but wanted to try to give all relevant info!

Thanks in advance
Ian

[Teapot1]

Yes calculations need to be done as that pipe run and diameter are quite some friction and headloss. No chance of re-site of the equipment? Do you know the make of the filter? If so buy another 600mm and use the two, that would give you a chance at getting your 12.5m3/h far more realistically than a single 750mm filter. Dont believe what the manufacturers say as flow rate, half it and thats closer. Glass media you say, Dryden Aqua's AFM ng, the best you can get.

[f1fanatic]

Yes calculations need to be done as that pipe run and diameter are quite some friction and headloss. No chance of re-site of the equipment? Do you know the make of the filter? If so buy another 600mm and use the two, that would give you a chance at getting your 12.5m3/h far more realistically than a single 750mm filter. Dont believe what the manufacturers say as flow rate, half it and thats closer. Glass media you say, Dryden Aqua's AFM ng, the best you can get.

Thanks for the reply Teapot.

I havent bought the new filter yet, and the old one is getting junked as its leaking, so I can go for a good brand (budget allowing)

So, am i right in thinking that the size of the filter is the bigger factor with the flow rate calculations rather than the pump manufactures flow rate charts?
The pump ive been looking at is 1.5cv and rated to 22m3/h, so on paper its over specced... but im struggling to calculate what effect the distance, head and possible bends might have on that flow rate

Unfortunately no possible way to re route without digging up the entire patio area around the pool....

[Denniswiseman]

Fitting a NRV on the suction side of the pump will give you constant prime, rather than 20/30 minutes which will cause problems with seals
Leaking joints don't help either and a gauge is easily replaced

[f1fanatic]

Fitting a NRV on the suction side of the pump will give you constant prime, rather than 20/30 minutes which will cause problems with seals
Leaking joints don't help either and a gauge is easily replaced

Agreed, which is exactly why i plan to fit a NRV in the new set up. The filter case itself leaks, not joints and ive tested the gauge to know its working fine, but due to the failing case of the filter its showing zero. All reasons why we are replacing everything... the main question I have is what spec of pump and filter do i replace it with?

[Denniswiseman]

Follow Teapot1 advice as he is knowledgable on filtration
Slower filtration and larger filter is best

[Teapot1]

I can do some headloss calculations just bear with me as I am my busiest just now. The NVR needs to be at the lowest point you can get it, hence asking if any of the kit could be re-sited eg mounting the pump lower. You do not need a big pump for filtration purposes as Dennis said slower filtration is better filtration hence the suggestion of 2 600mm filters in preference to one, something I have done quite often as the are gener3easier to site comared to a single large filter. It also means closing one filter at a time for backwashing gets a better backwash (20% bed expansion) with a smaller pump saving you a lot on electricity, going for a variable speed pump would be a smart move or a speed controller (variable speed inverter drive).
Are your skimmers on separate 50mm lines or combined? Likewise returns and how many?