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Discussion Starter · #1 ·
So I use 1/2" ID tubing in my loop:

CPU Apogee GTZ
2 x MCW60
Swiftech Microres

I think my pump isn't creating enough flow in this giant loop. So I was looking at the BlueLine 70 HD pump (or another high performance pump..)

Problem is, that pump uses 1" MPT threaded connectors. I was thinking of getting a much larger resevoir, and using 1" tubing from resevoir to the pump, then 1/2" everywhere else in the loop. Any suggestions as to what would be best?


373 Posts
I very strongly recommend that you not get a pump like that for a water cooling system. It's a very powerful pump. It uses 290W to run. That sounds awesome, but where do you think all the waste heat goes? The great majority of it goes right into your water. Your CPU puts 100W into the water at max load. It'd be like adding 2-3 extra CPUs to your loop to speed up your flow.

Never buy a pump that is more than you need. High flow rates are good, but provide diminishing returns. Eventually, higher flow rate can't offset the penalty you pay in pump heat. This pump is going to be well above the power that can be made up for by the flow rate it can drive. It's a bad move.

And I bet its noisy as hell. And it'll up your power bill a bunch.

Just try to get your flow rate over 1.5GPM and you'll be fine. The flow rated on the pump will not match this value, as they list flow rates for 0 resistance, but search the forums and ask around. There are much lower power pumps that'll do what you need more efficiently.

Since you've already got a MCP655 (which is probably enough, you might want to test your flow rate instead of buying a whole new pump) you can just get another one and rig it up in series. It'll boost your pressure and give you better flow rates.

Also, check out Martin's Flow Rate Estimator (linked to at the top of this page). It'll give you a ballpark figure of your flow rate if you can't measure it directly.

Premium Member
22,477 Posts
For a 1" MPT (Male Pipe Thread) you would need a "1 FPT (Female Pipe Thread) x1/2" barb fitting. If you can't find them locally you can get them at these 2 places.

..USA Plastics


But he's right that's just way to much heat dump from that Blue Line 70. I don't personally like going over a 40W pump heat dump, anymore then that I see no gain in CPU temp's and I use a jet block which thrive on high head and flow.

This is the pump I use..Iwaki WMD 20 RZ .It's a decent high head pump.It's AC so I re-lay it, or you can just have it on a plug strip and turn it on and off like that. The WMD is USA made, the MD is Japanese made, they are a little smaller and are supposed to run a little cooler. The nice thing about them are the are easy to over-haul and re-build. Stay away from any RX pumps they are just circulation with low head, not good for us. The 20RL is a nice pump with a little more flow then the RZ but with less head.

This is the top of the line.Iwaki RD 30 24v DC pump .. It's a 24V pump so you'll need a PSU with it and you want to run it around 18-20W or you end up with to much heat dump from it.

Or you could just get another D5 and run them in series, that way you'll get double the head and another 30-40% flow, plus if one dies the other will just keep pumping, redundancy is nice. I like running dual pump rigs.

Whatever gain you see in temp's will depend on the type of CPU block your running, more restrictive jet type CPU blocks see a higher gain then the more free flowing type.
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