There are plenty of cultivators who successfully feed compost teas and compost extracts through Blumat Watering Systems.
However, these cultivators generally have practices in place to minimize clogging. Clogging and failure of the Blumat System is the primary concern when using compost teas & extracts with a Blumat System.
These feeds are notoriously high in physical particulates as well as living organisms–both are factors that will increase probability of clogging in the system. Physical particulates will physically block the tubing and can stop flow, while living organisms tend to produce biofilm and other matter that can clog systems by themselves, or eventually grow large enough to produce a physical blockage on their own.
There are many precautions that can be taken when designing/installing/operating a Blumat Watering System to minimize problems when using nutrients/additives of any kind, including compost teas and extracts–more details can be found in this article.
So, the answer to this question is “yes,” but with some caveats. And in actuality, the absolute best results I have seen in commercial gardens have been facilities feeding pure water through their Blumat System, while supplementing compost tea/extract with hand-watering on top of the system.
As previously mentioned, physical clogging can occur when using compost teas and extracts. The clogs can even occur downstream of filters, due to increased biological activity in the water supply tubing. Biological entities can actually create more physical debris in the tubing downstream of filters.
However, my own primary concern when using compost tea and extracts in Blumat Watering System is on the more technical side of tea/extract-making.
Most cultivators making these brews do so in a vortex brewer or other compost tea brewer. These brewers create extremely oxygen-rich environments by repeatedly introducing air and oxygen into the mixture. These are referred to as aerobic environments, and are associated with beneficial biological entities.
Environments low in oxygen are anaerobic, and are typically associated with pathogenic organisms and other biological entities that negatively affect plant health/growth.
My concern is that because Blumat Watering Systems have such a slow/gradual flow rate, the compost tea/extract sits in the water supply tubing for an extended period of time. The water supply tubing in a Blumat System is an anaerobic environment. While I have not done or been a part of a study evaluating the biological profile of a tea before/after entering a Blumat System, I’d be willing to guess the profile dramatically changes between the input and output of the system.
The tea may be brewed in an ideal, aerobic environment. The cultivator may even check the tea under a microscope to monitor the organisms present in the tea/extract. They may even confirm a strong presence of beneficials and an absence of pathogenic organisms.
However, if this tea/extract sits in anaerobic supply tubing (regardless if it’s 1/2″, 8mm, 3/4″, or some other size) for an extended period of time, the biological profile of the tea/extract is likely to significantly change–if the same tea/extract were evaluated on the output of the Blumat system, it is highly likely that the profile of beneficial organisms:pathogenic organisms has dramatically shifted.
Compost extracts and teas can be used successfully in conjunction with a Blumat Watering System–however, it is highly recommended to design systems with appropriate infrastructure (filters, larger tubing diameters, flush/purge valves, etc.) in these cases.
Compost teas/extracts may be brewed with the utmost diligence, but their profiles can quickly shift if they spend an extended time in the water supply tubing of the system.
It is my opinion that best practices are to feed water (with minimal additives/amendments) through a Blumat Watering System, and to supplement any additional feeds through hand-watering, foliar-feeding, or other delivery mechanisms that do not encourage pathogenic organisms to proliferate in the system and soil.