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How does a bathmate pump work

How does a bathmate pump work


For those who use a bathmate I would like to know how it works. The air pump draws air out which creates a vacuum. Does the same idea work with the bathmate?

Have you ever seen a bathmate? That rubber booty at the entrance to the tube effectively acts as the pump because as you compress it, it forces water out of the one way valve in the end of the pump. The more water you force out of the tube, the higher the pressure gets as the one way valve holds the pressure. So it really works by pumping out water not air.

The main problem with the system is there is no way to measure how much pressure you have pumped up to and I would say you can easily get up around the 10”hg level which can easily cause damage.

The primary goal of PE should be to make your penis as healthy as possible in both form and function. If you do that, increased size will follow.

There are pictures and instructions on the faq page at:
www dot bath-mate dot com

I copied and pasted this from the bath mate official website:

“2. Secondly, the design of the bellows (the rubber part of the Bathmate) does not allow you to exceed the negative pressure threshold of 0.4 bar. Compare this to the FDA (Food and Drug Administration in the United States) which states that any device that uses more than 0.56 bar of negative pressure in Penis Pumps must go through FDA testing and approval before it is allowed to be sold in the United States. Similar rules equally apply in Europe and all around the world.”

0.4 bar = 11 inches of mercury, approximately.
I have no idea if that is a lot or not. I will say that I’ve been using my bath mate 3 or 4 time a week, 20 minutes at a time, since the autumn of 2011, at maximum pressure and have not sustained any injuries, but then every penis is different.

Sleepy278 - what are the negative sides of using a bath mate?

For example:

- Is the fluid accumulation greater than that for an air pump?
- Are you able to do longer sets using the bath mate compared to a regular air pump?

I’m planning on eventually getting a bathmate myself, want to focus on length first. So I can’t say exactly how well bathmate itself works, or it’s specific pros and cons compared to other water pumps. But the main difference between a water pump and an air pump is, not surprisingly, the difference between the properties of air and water.

The most important property in this case is called compressibility. Air is highly compressible, which means that removing or injecting air into a volume cause only a minor increase in pressure. So high compressibility means that you need to remove a lot to get a large change in pressure. A substances compressibility is represented by what is called the bulk modulus. The short version is that the bulk modulus of water is around 20,000 times larger than the bulk modulus of air. What this means is that removing a very small volume of water will cause a very large change in pressure. This makes water pumping inherently safer than air pumping; because if you reduce the pressure by a large amount, your penis only needs to expand a small volume to bring the pressure down. By comparison, in air pumping you have to be very very careful not to create a vacuum that is too large, because the further expansion of the penis will do very little to drop the pressure and you could end up with broken blood vessels, fluid cysts in your skin, even open bleeding.

A man isn't measured by the size of his penis. A man is measured by his contributions to family, community, and society; and by how he treats others.


Thanks for the information. Is it fair to say that, because a smaller water volume needs to be moved to create negative pressure relative to air; over expanding of the penis (by that I mean the fluid accumulation which causes temporary volume increase) is less in water relative to air? Take two scenarios:

Air pump at 2 Hg, high volume of air removed
Water pump at 2 Hg, low volume of water removed

The negative pressure is equal, the volume of fluid displaced is not. There is less room for expansion in the water pump relative to the air pump because the volume available for the penis to expand in is less. This should mean that fluid accumulation with a water pump is less than that of the air pump in an identical situation.
Is this reasoning accurate?

Bathmate versus air pump


Regarding bathmate (or water pump) versus regular air pump which is better in terms of:

1. Fluid retention (does the water pump cause more fluid buildup)
2. Seal (does the water pump’s seal hold better)

I am thinking of designing a mini water pump (or mini bathmate) so I would like to know whether the bathmate is ‘better’ than the existing air pump



Also can you let me know what the valve type is?

You don’t need a bath mate nor do you need to invent a new bath mate if you want to water pump.

Just a few threads down from yours:

Water Pumping inexpensively

See also:

sparkyx - New look at Water Pumping

Re your questions regarding water vs air, see also:

Water Pumping Basics

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