Does the inlet/outlet size cause a problem?


New member
Jun 6, 2021
Sussex, UK
Hi! :) Completely new member here, so apologies is this is a really basic/obvious question, but we have a Bestway 18'x9' steel frame pool from Costco we bought a few years back.

We recently upgraded the sand filter and pump that came with it to the same make (FlowClear) but a larger capacity (we did this under the assumption that because we're pushing the water up higher to the solar mat that's on our shed roof, we needed more "oomph" to do it).

Anyway, now we've ended up with two pumps and we thought we could have them do different tasks - have the larger pump do the filtration and the smaller one work on just the solar mat (as it worked anyway, we just tried to make it better - can you tell we are just winging a lot of this and wish I had found this forum earlier? :LOL:). So for that I thought I'd probably end up running some pipes and have dual connectors into the inlet and outlets to split between the two pumps.

OK, so onto my actual question... The Bestway pools inlet and outlet have a diameter of about 26mm/1" with the flexible pipes we being about 38mm/1.5". Would the 1" diameter section, which would split out to something I can step up to the larger diameter pipes for two pumps, cause a "pinch point" and and limit the capacity of the larger pipes? It doesn't seem to me a problem right now for just one pump, but I don't know about adding a second pump into the mix. Does anyone have any recommendations on hooking things up in such a way for a Bestway pool?

Many thanks!


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

Having two pumps pull from the same suction and/or return to the same outlet will not work. They will interfere with each other’s flow and one will run dry or cavitate. Each pump needs to have its own dedicated suction and return.

Use one pump. Two will not make it better.
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