eheim air pump low pressure

[ScareCrow]

Hi All,

I've got a second hand eheim 400 air pump that to me seems to output quite low pressure. I've got two hygger piezo air pumps that came with air stones. I've tried to power the air stones using the eheim pump and nothing comes out, where as the hygger air pumps run them fine.
I've taken the eheim pump apart and nothing seems out of place, the diaphragms seem supple still and it's not producing much noise like air pumps do when the diaphragms need replacing.
Is this normal? I can't find any pressure specs for the eheim but notice it does normally come with an eheim diffuser so I'm wondering if this is less restrictive compared to the normal air stones.

Thanks in advance.

 

[JohnCooke]

I have the same airpump. If you connect it up to 1 or 2 airlines, without airstones, and put the airlines in the water, is it producing bubbles? [Do ensure you have non-return valves fitted before trying this!]

 

[ScareCrow]

I have the same airpump. If you connect it up to 1 or 2 airlines, without airstones, and put the airlines in the water, is it producing bubbles? [Do ensure you have non-return valves fitted before trying this!]

Yeah air comes out of both outlets fine and I forgot to mention both flow rate controls also work as expected.

 

[Maf 2500]

How old are the airstones? Might be partially clogged, and the Eheim not producing enough pressure to overcome this. When I researched the piezo air pumps a while back I was very surprised by the very high air pressure compared to low air volume pumped in this design.

 

[ScareCrow]

The air stones are brand new.
I was thinking that the piezo air pumps may produce more pressure than the eheim but I couldn't find any specs on pressure output for the eheim so not sure. Surprised it can't push air through the air stones though. I even tried connecting both outputs to a single stone but nothing.

 

[Maf 2500]

How deep are the airstones? have you tried holding them just under the water surface? Would make a difference if it is pressure related.

Might be worth measuring the volume of air output by the Eheim, which would likely be seriously reduced if it is faulty. (Time how long it takes to fill a submerged container of known volume)

 

[ScareCrow]

Just under the surface it will fizz slightly any deeper and there's no output at all.
Good idea about the volume output, I'll test and see how it compares to the specs.

 

[bazz]

There has to be a problem and they are quite basic so might be worth replacing the diaphragm, having said that they aren't cheap at 16 quid so would be an expensive trial and error if it's not the problem.
Mine has been running trouble free non stop for four years now.

 

[ScareCrow]

they aren't cheap at 16 quid

This is the reason I thought I'd ask first 😂
They're £15 on eBay but I'd need 2, so could almost buy a new pump for that, which is really wasteful.
The fact it's not noisy does make me think it's not the diaphragm though. All my previous air pumps became horrendously noisy as the diaphragms hardened.
I need to try Maf 2500s suggestion and measure the output.

 

[trent315]

I bought a cheap air pump from The Range. Please, please, please let me know what can I buy that won’t be as noisy. I know they make noise, but this sounds bad. It makes buzzing sound at times and I don’t think thats safe to use.

 

[ScareCrow]

I bought a cheap air pump from The Range. Please, please, please let me know what can I buy that won’t be as noisy. I know they make noise, but this sounds bad. It makes buzzing sound at times and I don’t think thats safe to use.

Piezo air pumps are probably the quietest small air pump, certainly that I've used.
What dimensions are the tank and is it your only form of filtration or additional?

 

[trent315]

It’s a 60L hexagonal and I have a filter and some java fern, duck weed, anubias and a few more plants. I do use the air pump as often as I can, but it makes that silly buzzing.

 

[ScareCrow]

It’s a 60L hexagonal and I have a filter and some java fern, duck weed, anubias and a few more plants. I do use the air pump as often as I can, but it makes that silly buzzing.

A piezo air pump should be fine for that if you're just supplying some additional water movement. I've got 2 of these though they've nearly doubled in price so might be worth having a look around. The pumps themselves are practically silent, you only hear the bubbles breaking at the surface.