Thread: Amalgam UV owners - how long does yours need to stay on per day?

...so I plopped a 40w Amalgam UV in the up pipe of the bottom drain for now. But wow, it has made the water crystal clear. Definitely worth the money. 40w Amalgam compared to 36w (no amalgam) I used last year is like night and day.

That said, now the pond is clear I'm experimenting with how long I need and 40w Amalgam UV on for in a normally stocked 2660 pond.

I've gone from 24hrs a day to 6hrs on 6hrs off, for now. Every pond is different but, I'm curious as to what others do, to take some of the guesswork out...

Originally Posted by GDL

I leave mine on 24h from the time I notice algae in the spring until about October.
Seem to remember reading that every on/off cycle reduces its lifespan by a day - now that may be rubbish and I can't for the life of me remember where I saw it.

I have an 80W amalgam that sits externally and is fed by a variable pump. I'd love it to be air driven but the reality is it works as it does. I can therefore vary the rate of flow and switch both pump and UV on/off separately from the main pond. The pond is 14000 litres airlift powered so without it running it only takes 58W. With it running, it adds about 100W.

It gets removed (along with the quartz) in winter to protect it from any freezing but in spring it's reassembled and I'll use it periodically until the temps start warming up and the pond starts looking hazy. After that it's usually on for most of the time but at the same time it can be off for a week and the pond will remain clear (in full sun). It usually takes a day or so to clear the pond.

The advantage of 80W is everything gets very nuked and as it's sat in a 4" pipe, it can cope with a decent flow rate and still be effective. Turning down the flow rate simply makes it more effective or copes with any efficiency drop off.

Originally Posted by GDL

I leave mine on 24h from the time I notice algae in the spring until about October.
Seem to remember reading that every on/off cycle reduces its lifespan by a day - now that may be rubbish and I can't for the life of me remember where I saw it.

If you remember the old fluorescent tubes, they lasted quite a while being switched on/off. It's usually a cheap ballast (the power supply) that dies with switching on and off.

I have a dead amalgam ballast that apparently was only a 2 years old, so there may be some truth to that, especially as I have have two amalgam bulbs that have out lived the ballast. but...
I haven't taken it apart yet, however everything I can find suggests that the ballasts are identical to normal UVs,.it's just the bulb that's different.

...which also implies that if you changed the plug for the bulb on a normal UV could you convert any UV to take an amalgam bulb.

Originally Posted by Alburglar

I have a dead amalgam ballast that apparently was only a 2 years old, so there may be some truth to that, especially as I have have two amalgam bulbs that have out lived the ballast. but...
I haven't taken it apart yet, however everything I can find suggests that the ballasts are identical to normal UVs,.it's just the bulb that's different.

...which also implies that if you changed the plug for the bulb on a normal UV could you convert any UV to take an amalgam bulb.

And the little cylinder that you replaced in the lamp hold itself in the old days.

I personally turn mine on when the water starts discolouring and then off when it has cleared up. I don't really see the benefit of it on 24/7 if the water is clear In summer I try to remember to stick it on once a week for 24 hours to keep the bio off the drum mesh though.

Originally Posted by samp09

I personally turn mine on when the water starts discolouring and then off when it has cleared up. I don't really see the benefit of it on 24/7 if the water is clear In summer I try to remember to stick it on once a week for 24 hours to keep the bio off the drum mesh though.

If you select the bulb to be a Phillips T5 compatible you can replace the ballast for not much money.