Hi all. I'm new to this forum and this is my first post. I tried to do a search on this topic, but nothing relevant came up. Also, not sure if this is the right section to post this in, as there is no spa-specific pumping issues section.
Anyway, I have a pretty old Marquis spa (I believe it is called the "Euphoria") that is otherwise running well. The spa has two pump circuits -- one for the "therapy seat" and the center inlet (and also the heater) and one for the other seats around the tub. There are dual drains for each circuit, so 4 total suction fittings. Each of the circuits also has a filter near the top of the waterline that is sort of like a skimmer. Recently though, one of the pump circuits (the heater circuit) has developed a suction issue that has me perplexed. One of the two suction drains has lots of suction, while the other has almost none. The drain that works is closest to the pump. I am not sure how this is all plumbed in this area, since I cannot get to it, but I believe most dual drains are just two lines merged into one, without any sort of check valve or anything. I also don't know how the filter canister is plumbed to the two suction fittings. So, I am assuming there is some sort of blockage between the two drains. However, I tried snaking the line from the bad drain and it seems to go a long way (possibly all the way to the pump), so I'm confused.
I cannot find any plumbing diagrams for this spa and I don't have a way to look inside that part of the spa enclosure, since the spa is installed in a recessed pad, which blocks the panel on that side. So I don't know how the two suction fittings tie together and how they are tied to the filter.
Has anyone seen anything like this before? Any ideas?