Pump Pressure Keeps Maxing Out

[ben_and_ali]

Hi,

My pump is supposed to operate at 60 KPa when filtering. Recently it has been quickly rising to 120 KPa, at which level the suction is much lower due to I suppose the resistance in the system which is also causing the pressure to go up. I have repeatedly emptied my leaf catchers which drops the pressure by maybe 5 KPa for about 2 minutes, and I also have repeatedly backwashed the filter, with similar effect.

I'm a bit worried about the effect on the pump constantly operating at such high pressure, and also the fact that the pool isn't getting filtered very effectively.

What could possibly be causing this extreme hike in pressure that cannot be fixed by emptying leaf catchers or backwashing???

Please help?!?!?!?

Oh yeah - filter is a sand filter Waterco T600. Big round thing. Pump is an Onga LTP750.

[pool care]

Hmmm... Firstly you should check the sand in the filter. Open up the saervice cover and visually check for clumping, silting up or general gunk.

Have you had an abnormal dirt load too?

[ben_and_ali]

Hi Pool Care

I've just had a look at the filter and I'm almost positive there isn't a service cover. It's just a big round grey thing, no windows, no nothing. On top is the valve set up. I just unscrewed all the screws I could see on that and still couldn't see into the filter... so no sand report unfortunately.

I did have an abnormal dirt load recently - I was doing the post winter clean up, and there was quite a lot of muck on the bottom of the pool. I got most of it out with the scoop, but there comes a point when this is no longer efficient! So I filtered it. Could this have done long lasting damage to the filter? Can it be worked out of the system?

btw the landlord said he changed the sand this time last year, and it should only need doing every 3 - 4 years. But he's been wrong before...

[pool care]

it should only need doing every 3 - 4 years

That is about right. The quartz can usually last at least 5 years.

How low have you seen the pressure high? A typical 1Hp pump will move 17m3 / hr and a typical 60cm sand filter will filter 15m3 / hr. With a new bed of filter sand it is expected that the pressure will be high because you are working the filter at its limit.

The manufacturers' claims for your equipment are as follows:

• The Aquaco T600 filter can filter up to 226 litres per minute
• The Onga LTP750 can pump up to 250 litres per minute at a 5m head

So you are pumping faster than your filter can comfortably clean. High pressure is normal.

[ben_and_ali]

Thanks again for your response Pool User.

I've been running the pump for a couple of months and it has run with a constant 60KPa in the lines, and it works very well - suction is high and the creepy crawly flies around. I am assuming this is the steady state which matches the discrepancy in flow rates of the pump and filter that you stated.

However, now it is running at about 120-150 KPa, and the suction has dropped right down. The creepy crawly barely moves. I'm certain that something has gone wrong! Has anyone else had a similar experience, and know what the cause might be?

I'm sure it is a filter issue because if I pump to waste the pump works fine.

[pool care]

I've been running the pump for a couple of months and it has run with a constant 60KPa in the lines

Almost certainly a filter issue. You need to disconnect the pipes from the multiport valve and remove the collar that holds the valve onto the filter. Check the picture of your filter if need be. Then lift the valve off the central pipe (that leads to the lateral assembly).

Plug the pipe or cover the opening to prevent getting sand in it.

Visually inspect the sand. Grab a handful, dig down some and grab some more. Check the level. Take photos if possible or describe what you find in detail.