Spectra 380c - backflush water is brackish instead of fresh, tests > 1000ppm.

[WombatWhiskers]

I'm stuck, can't work out why supposedly fresh backflush water is testing > 1000 ppm, tastes quite salty.

I have pickled, disconnected membrane and Clark pump. So I can easily sample the flush water right where it exits the pre-filter housings.

Solenoid is acting when flush cycle is started at the panel. Only pump #1 is active.

First I removed and inspected the check valve that is supposed to prevent sea water from invading when the fresh water line is pressurized via energizing the backflush solenoid. I see no issues with check valve, just a faint film of green biofilm (see photo).

Reinstall check valve, test flush water. 1st bucket tests ERror tastes salty. So I set Spectra intake valve = blocked, so only possible source of water is shore water via solenoid. My third bucket of 'backflush water' collected after prefilters tested 850ppm, 2nd bucket about 700. Vs. shorewater 140, so I decide there must be a solenoid malfunction which might be restricting the volume of freshwater enough that check valve opens.

I demount, inspect 24V solenoid valve (see photo). Coil functions, valve operate correctly as best I can tell by blowing on input.

It is a pain to reinstall, deinstall the backflush assembly, so before doing that I'm hoping someone can point to where I have gone wrong?

[Kenomac]

Contact cf member tellie. He's the pro on this site when it comes to spectra. He is on my friends list if you need to find him.

[Tellie]

Originally Posted by WombatWhiskers

I'm stuck, can't work out why supposedly fresh backflush water is testing > 1000 ppm, tastes quite salty.

I have pickled, disconnected membrane and Clark pump. So I can easily sample the flush water right where it exits the pre-filter housings.

Solenoid is acting when flush cycle is started at the panel. Only pump #1 is active.

First I removed and inspected the check valve that is supposed to prevent sea water from invading when the fresh water line is pressurized via energizing the backflush solenoid. I see no issues with check valve, just a faint film of green biofilm (see photo).

Reinstall check valve, test flush water. 1st bucket tests ERror tastes salty. So I set Spectra intake valve = blocked, so only possible source of water is shore water via solenoid. My third bucket of 'backflush water' collected after prefilters tested 850ppm, 2nd bucket about 700. Vs. shorewater 140, so I decide there must be a solenoid malfunction which might be restricting the volume of freshwater enough that check valve opens.

I demount, inspect 24V solenoid valve (see photo). Coil functions, valve operate correctly as best I can tell by blowing on input.

It is a pain to reinstall, deinstall the backflush assembly, so before doing that I'm hoping someone can point to where I have gone wrong?

If you are testing 1000+ PPMs at the brine discharge then you are either drawing salt water in to the system or you are not flushing long enough. The quickest test is to shut off the intake thru hull before flushing. Then run a flush for five minutes then test. You should be around 800PPMs or below. If not run for another minute and test, repeat until you get 800PPMs or below. You also want to do a flow test on your fresh water input at the watermaker. If your test shows less than 1.8-2gpm then you are not getting enough flow to the feed pump and it is creating a vacuum and drawing salt water from the thru hull. Your feed pump may be demanding more than your boats fresh water pump can supply. It doesn't take but a very little amount of sea water mixed with fresh water to have your brine discharge quickly go over 1000PPMs. Also it can take more than five minutes to get all of the salt water purged from the membrane. It takes a good bit of water to fully flush a membrane because of it's design and there is always a little residual salt left after only a five minute flush. If you are doing regular flushing, 800-1000 PPMs at the brine discharge is not unusual or harmful.
It doesn't make sense that if you are using pressurized shore water at 140 PPMs to flush, your thru hull is shut off, and you are testing the water before it goes through the Clark pump and membrane and still getting more than 1000PPMs. You have to be drawing salt water from somewhere. Test the shore water at the charcoal filter housing before the feed pump intake (let your boats pressure pump supply the pressure) and then test it after the feed pump output (this time with just your boats pressure and the watermakers feed pump running). If it is higher on the output you are certainly drawing salt water in from the thru hull somehow. Either a bad check valve or a bad thru hull.

[WombatWhiskers]

Thanks heaps. I've just filed your guidance in my Spectra Troubleshooting archive folder.

I will test after I put the flush system back together today (after several improvements for serviceability). Two likely culprits are:

1. Single pump domestic supply < Spectra feed pump demand
2. Faulty check valve (sure looks OK)

Easy solution to #1 is for us to always turn on domestic Shurflo #2 for backflushing. I was running only Shurflo #1 because I didn't want to take time to prime Shurflo #2. These two (of three) pumps are normal domestic supply - controlled by staggered external pressure switches. #2 kicks in when demand requires.