Back pressure in liquid ring vacuum pump liquid seal supply line

[tomjelly]

Was talking to a dentist friend who told me they are getting air in their water coming out of sink faucets. They have a liquid ring vacuum pump, and the water supply is used for the liquid ring. I'm thinking the pump must be pressurizing it's water line, a big no no. The vac system is working properly. I would think that it is possible that a clogged inlet filter on the pump suction line would be the only thing that could be the problem, or am I missing something? Seems there should also be a check valve in the pump liquid ring supply line to prevent this, and that without a check valve it is conceivable that the nasty stuff being suctioned could theoretically be introduced to the water supply lines. Am I wrong?

 

[eKretz]

I've been getting this recently too. Noticed that when I went to get some cold water for cooking it looked foggy as hell. Let it set for a few minutes and it cleared right up. Air entrapped in the water. Could just be the water supply. We have city supplied water, it may be coming through the pipe that way. I've read that in winter this is a common occurrence.

A check valve is probably a good idea anyway.

 

[tomjelly]

The pump draws from a tee right by the water heater inlet. This is large pockets of air, so the faucet nearest the water heater blasts water all over the place till the air is expelled. I spoke to them today about adding the check valve and was also relieved to hear they use purified bottled water at each chair station for the drills and rinse, but told them that the regular sinks should never have air in the line. They then said the problem started after a recent hard freeze, worse than in many years around here, which they didn't mention before, but might be coincidental. Told them to shut off all water and see if the meter is moving, but air in the line would sure be an odd symptom of a pressurized water line leak...