FAQ
Do the low pressure UV systems destroy all the chloramines?
No
Low pressure bulbs are monochromatic, and deliver only one type of wavelength UV-C (254nm). Low Pressure UV systems have a lower performance in destroying the chloramines compared to the medium pressure UV systems, which are polychromatic lamps with absorption capable of destroying the 3 types of chloramines (mono, di and tri chloramines).
Do the low pressure UV systems destroy monochloramines and avoid the creation of di and trichloramines ?
NO
A swimming pool is a closed environment where the water will pass through the unit a couple of times per day. Contact time between organic compounds and free chlorine is long enough to allow the creation of di and trichloramines. Even if you work on the monochloramines, you will still have di or tri chloramines in your public pool or spa.
Are the low pressure UV lamps monochromatics lamps ?
YES
Low pressure lamps emit only one type of wavelength. They are very active on the monochloramines, but far less active on di and trichloramines
Are chemical reactions well understood with the use of polychromatic medium pressure bulb?
NO
Medium pressure UV bulb is the best proven technology for the destruction of chloramines. MP UV bulbs are emitting the following wavelength:
• 244nm for monochloramines (NH2Cl)
• 294nm for dichloramines (HNCl2)
• 336nm for trichloramines (NCl3)
Delta’s UV systems do not emit wavelength under 240nm due to special quartz sleeve. There is no possibility to generate any harmful by products.
Do the low pressure UV systems decrease the trichloramines in the air ?
NO
Low pressure UV bulbs are less efficient on trichloramines and cannot work actively on trichloramines. Only medium pressure is truly efficient on reducing the trichloramines in the water and in the air. As a consequence, the reduction of trichloramines in the air results in the reduction of trichloramines in the air.
Does UV treatment change the pH, the quantity of chloride, TOC (Total Organic Carbon) ?
NO
PH, quantity of chlorides, TOC levels do not change during the UV treatment.
Do low pressure bulbs consume less electricity ?
YES
However, because of an electronic ballast and power regulation, medium pressure bulbs allow better electricity consumption through power management.
Do low pressure bulbs allow a better ratio efficiency /electricity consumption?
YES / NO
30 to 35% of the total energy displayed in the low pressure UV bulb is used to provide UV-C. Medium pressure bulbs provide 15% of UV-C but also provide different other wavelength which are efficient to remove chloramines. With the addition of power regulation, the unit will optimize electricity consumption depending on the flow rate and life-time of the lamp.
Do the low pressure bulbs have a life time up to 2 years?
YES / NO
According to UV bulb manufacturers, life time of a bulb is comprised between 9,000 hours up to 16,000 hours, or 1 to 2 years. However, you will need more low pressure bulbs to obtain the same results as medium pressure treatment. However, medium pressure UV bulbs, due to power regulation, can attain a life time up to one year.
Does a low pressure defective lamp prevent the unit functioning correctly?
Yes
When a lamp doesn’t work, the UV dose necessary to disinfect is not delivered. Therefore disinfection / dechloramination is not performed.
Do low pressure UV systems generate THMs?
NO
Whatever the UV bulb technology used, THMs can be created if certain factors are not properly managed. Low and medium pressure doesn’t create THMs if the UV dose is correctly adjusted, if the UV-C wavelength provided are over 240nm (which is the case for medium pressure) and if the other parameters in the pool are not exaggerated.
Do medium pressure UV systems generate THM?
NO
THMs are created only if certain factors are not properly managed. The UV dose must not be exaggerated, UV-C wavelength must be over 240nm (Medium pressure UV-C lamps allow that) and all other parameters must be respected. In normal use and condition, medium pressure UV systems do not generate THMs.
Does a low pressure UV system restrict flow on the piping system?
YES
Z or U shape of low pressure UV system generate minimal restriction compared to the medium pressure systems which are designed straightforward (for those Z or U shape systems, restrictions are not measurable because they are below the detection limit even if you use a bypass).
Can a UV system allow savings in fresh water renewal up to 50% ?
YES / NO
Each pool is its own case. Fresh water savings can be from 25% up to 60%. It depends on the bather load, the kind of treatment, the air treatment, design of the pool, technical specs, etc.
Références : 
Circulaire DGS du 22 février 2008
Ministère de la Santé AFSSA
Technologies UV
Technologie BIO-UV
Toutes les références de chimie
Yinn et Margerum, Inorg. Chem,1990
Hamel, 2007
Oesterholt, 2009
Rasmus Andersen, 2009
Gestion de la globalité d'une piscine
Cassan et Col., Chemosphere 2006
Hamel, 2007
Recommandations AFSSA dans le traitement de l'eau
