Need to Install a DPT Above the Liquid Service Level

Why don't you mount the DP transmitter below the taps, which keeps any air from collecting at a 'high' point, and run the transmitter's 4-20mA output to a loop powered digital display which can be mounted anywhere that you can get wire to?

If accuracy is not important,and you simply need an indicator of when to change filter,

a differential pressure switch with an audible alarm and/or light would suffice and be more economical and relaible in the long term.

Determine the desired differential,order a switch with either a fixed differential or

adjustable to suit your application.

It took me a week to find this. I couldn't remember that I'd saved it as 'bubble pot'.

The graphic below shows how a bubble pot (a condensate pot rated for the line pressure/temperature with a bleed vent/valve to release accumulated air/vapor/gas) is piped/plumbed.

I've never had to use one, and I can not say how well they work.

I'm actually doubtful that the accumulation of air/vapor/gas will not induce a head pressure error. It seems to me that the transfer of pressure by a bubble pot is different than a steam condensate pot.

Both a bubble pot and a steam condensate pot will maintain a constant, static liquid head pressure (any liquid higher than the side tap will drain back into the main pipe). But a steam condensate pot has steam pressure on top of the static liquid head pressure. A bubble pot requires the impulse line liquid pressure to pressurize the air/vapor/gas cushion, and exert the impulse tube pressure onto the static liquid head.

Yeah, I know, exerted pressure in a closed system is exerted equally in all directions, but somehow in (relatively) low pressure (inches water column) applications, trapped air manages to produce head pressure errors.

If the pipe taps are at ~45 deg downward (conventional for liquids) angle, that will tend to minimize air release into the impulse tubes.

I'd appreciate hearing from someone's who's actually done this to see how accurate the pressure transfer is and whether there's any added maintenance involved.