I have a heat pump which is working just fine but when it kicks on there is a sound like liquid being slurped up a straw (starts low & pitch gets higher until it stops). Don't feel like paying $90 for a service call to find out it's nothing so thought I'd ask here. Thank you for any assistance you can provide.

If the unit is performing well then the problem is probably not that severe. Is it the unit outside that is making the noise or the line set that comes into the home or the inside unit itself.

It is inside the home that the noise is occurring. I tend to agree not a disaster but also wanted to see if any ideas so it doesn't become one later.

Sounds like the indoor coil feed circuit. Usually a expansion valve is in place on most heat pumps and most expansion valve are either a self equalizing or a total shut off design. You might have a total shut off design valve that the check valve inside the expansion valve is not working properly allowing it to bleed in the off cycle. This will cause a noise similar to what you are hearing. While the valve is not operating as designed as far as the check portion in the valve no harm is being done and you can continue to use the system as is. If the system was under warranty then I would say call them for a free repair. When you have to pay for this yourself it might cost up to 400.00 for the repair or even more depending upon part mark up and labor rate.

Okay, that sounds about like what I thought (not all the technical parts, but a vacuum or feed line that wasn't quite sealed). Warrantee in place on parts but not labor & the visit charge is $90 off the top. We'll get to it sometime this summer I think.

Thanks a lot!

No problem. Glad to be of service.