# Siamese Pressure washers 1 unloader **URL:** \ **Category:** Newbie Questions\ **Created:** [April 7, 2024, 12:38am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238 "2024-04-07T00:38:17Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![baldwin30](https://pressurewashingresource.com/community/letter_avatar_proxy/v4/letter/b/ee7513/32.png) [@baldwin30](https://pressurewashingresource.com/community/u/baldwin30)\ **Post date:** [April 7, 2024, 12:38am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/1 "2024-04-07T00:38:17Z")
Hi everyone, Starting this season I’ve decided to run two 4.5 GPM pumps together with a Siamese kit (Same pumps, Engines and unloaders). One pump I ran last season, rebuilt this spring however its not running as much PSI as the new pump. They ran normally for the first few days with good flow and consistent pressure. I installed two new unloaders on both machines however they seem to be fighting with each other, even with the check valves installed upstream on the Siamese kit. It runs fine for a few hours then seemingly randomly acts up. The unloaders continually cycle and sound like little jack hammers going off. Both pumps run fine independently with normal pressure when unhooked from the Siamese kit. My question is has any one installed one unloader for two pumps to run off of? I was planning to run it after the two check valves to try and solve the issue of the unloaders constantly kicking In and Out and competing with one and other. ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [April 7, 2024, 2:11am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/2 "2024-04-07T02:11:07Z")
This is a topic that is discussed every so often and always ends the same. That set up doesn’t work. Take the two 4.5s and sell em and buy a dedicated 8gpm machine. ---
**Author:** ![Thor1911](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/thor1911/32/41758_2.png) [@Thor1911](https://pressurewashingresource.com/community/u/Thor1911)\ **Post date:** [April 7, 2024, 6:37am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/3 "2024-04-07T06:37:47Z")
What would happen if he had both pumps running to one unloader? like a zk1 ---
**Author:** ![Infinity](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/infinity/32/30829_2.png) [@Infinity](https://pressurewashingresource.com/community/u/Infinity)\ **Post date:** [April 17, 2024, 10:50am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/4 "2024-04-17T10:50:19Z")
Why is one of the pumps running lower pressure? Does it have a smaller motor? Both unloaders should be set to the same pressure. This is a “weakest link” scenario. Your max pressure will be dictated by the less powerful machine. I’m guessing the jackhammering is happening from the unloaders bypassing as slightly different pressure points. Going to a single unloader should theoretically solve the issue. But I’d probably stick with a trapped pressure (vs. flow-actuated) unloader, and set it to the lower pressure. The zk1 might act unpredictably with two pumps feeding it. But I’m in agreement with @mwpws. Invest in a 8gpm machine. ---
**Author:** ![dcbrock](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/dcbrock/32/38857_2.png) [@dcbrock](https://pressurewashingresource.com/community/u/dcbrock)\ **Post date:** [April 18, 2024, 12:55am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/5 "2024-04-18T00:55:51Z")
Alex good grief where have you been? ---
**Author:** ![baldwin30](https://pressurewashingresource.com/community/letter_avatar_proxy/v4/letter/b/ee7513/32.png) [@baldwin30](https://pressurewashingresource.com/community/u/baldwin30)\ **Post date:** [April 18, 2024, 12:03pm UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/6 "2024-04-18T12:03:32Z")
Thanks for all the Input everyone. I’m going to try the single unloaded for my next week of projects and will post an update. I’m planning to go the 8 GPM route this summer. ---
**Author:** ![Infinity](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/infinity/32/30829_2.png) [@Infinity](https://pressurewashingresource.com/community/u/Infinity)\ **Post date:** [April 18, 2024, 11:32pm UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/7 "2024-04-18T23:32:25Z")
Lol. I guess I just sorta lost interest? Bigger issues on my plate for awhile there. But I hope to be a little more present now. ---
**Author:** ![dperez](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/dperez/32/21232_2.png) [@dperez](https://pressurewashingresource.com/community/u/dperez)\ **Post date:** [April 19, 2024, 2:59am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/8 "2024-04-19T02:59:20Z")
Glad to see you back! ---
**Author:** ![PMG](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/pmg/32/36519_2.png) [@PMG](https://pressurewashingresource.com/community/u/PMG)\ **Post date:** [April 20, 2024, 1:16pm UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/9 "2024-04-20T13:16:44Z")
Yeah, @Infinity you’re an appreciated contributor on this forum. ---
**Author:** ![Innocentbystander](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/innocentbystander/32/36516_2.png) [@Innocentbystander](https://pressurewashingresource.com/community/u/Innocentbystander)\ **Post date:** [April 21, 2024, 3:20am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/10 "2024-04-21T03:20:50Z")
Hey Alex and gang ---
**Author:** ![baldwin30](https://pressurewashingresource.com/community/letter_avatar_proxy/v4/letter/b/ee7513/32.png) [@baldwin30](https://pressurewashingresource.com/community/u/baldwin30)\ **Post date:** [May 12, 2024, 1:39pm UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/11 "2024-05-12T13:39:40Z")
Been running this setup for the past few weeks without issues, using only one unloaded for the two pumps seems to have made the difference. I’ve put approximately 50 hours on it so far with the two pumps running. I use only one pump to downstream for the time being. No unloader hammering anymore. Thanks for the input everyone ---
**Author:** ![Davey](https://pressurewashingresource.com/community/letter_avatar_proxy/v4/letter/d/958977/32.png) [@Davey](https://pressurewashingresource.com/community/u/Davey)\ **Post date:** [September 11, 2025, 10:43pm UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/12 "2025-09-11T22:43:16Z")
Way to go with what your gut tells you!! I had a similar issue I’ve been running two engines two pumps one pump with a little bigger and they were both about 4,000 psi one was four GPM the other one was five and a half GPM so everything was working great especially when it came to using the surface cleaner I got the right nozzles and I’m cleaning driveway after driveway after driveway and if I use the right J-Rod everything is lovely well I started having unload a problems on both of my engines it seem like and I started having hoses burst equipment break so I bought a really nice unloader and solved the problem no more pressure build up and then boom and then I thought how about I run just a line coming out of the pumps and to my splitter and check valves and then put the unloader in front of that It can handle up the 13 or 20 GPM so why not? So that’s what I did and everything is lovely That’s how I should have done it in the beginning that was 9 months ago ---
**Author:** ![baldwin30](https://pressurewashingresource.com/community/letter_avatar_proxy/v4/letter/b/ee7513/32.png) [@baldwin30](https://pressurewashingresource.com/community/u/baldwin30)\ **Post date:** [September 12, 2025, 10:59am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/13 "2025-09-12T10:59:41Z")
Hey Dave, good to hear that! Yes I ran mine this way for all last season. Worked well, I liked it for the fact that I could conserve water if I didn’t need all 9GPMS of the two running at once. Turn one off and now it’s just 4.5GPMS ---
**Author:** ![Drocks](https://pressurewashingresource.com/community/letter_avatar_proxy/v4/letter/d/838e76/32.png) [@Drocks](https://pressurewashingresource.com/community/u/Drocks)\ **Post date:** [September 5, 2026, 12:22am UTC](https://pressurewashingresource.com/community/t/siamese-pressure-washers-1-unloader/38238/14 "2026-09-05T00:22:26Z")
Can anyone confirm for me that this is a better way to plumb when running a 5.5 and an 8 gpm combined, out to HP checks on all 1/2’ output? I have gauges on both before check valves and another after and configure pressures as close as possible…but I have also noticed that sometimes after a few hours something seems to change or vice versa. After a couple hours all of the sudden I have much more flow than previously, which tells me something hasn’t been running right. Any thought? Can anyone confirm the same would apply given much different gpms on the machines? Should I leave the trapped pressure unloaders in place at machines and simply add another 1/2’ high flow unloader after these? Seems like I will need them given the gpm difference?