Everyday, our Sales and Technical Support teams field this question from our Customers: "Which SeeLeveL tank sender do I need?". There are a few things to consider when choosing the correct sender for your tanks.
The height of your holding tanks will play a big factor in determining which Senders you need. After measuring the overall height, we then have to consider the installations requirement for the SeeLeveL Tank Senders. We recommend that the senders be installed 1/2" to 3/4" from the top and bottom of the tank. This gap ensures that the sender can read properly thru the tank wall as the corners or rounded edges of the tanks can be too thick for the sender to read thru. We can then find our sender length by subtracting the total spacing from the overall tank height. If you choose a 3/4" gap, then you would subtract 1 1/2" from the overall tank height.
This is not a static formula that can be used on every tank. With some fresh tanks, the outlet for the pump feed may sit more than 1 inches above the bottom of the tank. Your water pump may begin to suck air before the tank is complete empty. In these cases, we want to install the fresh tank sender above the outlet for the pump feed. This will ensure that the monitor reads 0 before the pump begins to suck air.
Ultimately, once we determine the length of sender that we need, we can begin to choose which sender will give the best resolution for the sender space available. In order to get the best reading possible, we want as many read segments (referred to as pads in the manual) as possible on the tank.
These segments are the dark green rectangles located on the left side of the sender. The segment length varies with each model of sender. The 710JS has a total of six 1" segments. The 710ES has a total of eight 1 1/2" segments and the 710SS has a total eight 2" segments.
During installation, you will most likely need to cut the senders to length. As shown in the picture below, you can ONLY CUT BETWEEN THE READ SEGMENTS. This will play a factor in choosing which sender will give the best resolution. You can remove as many as 2 segments from the 710JS and 5 segments from the 710ES and 710SS senders.
Again, our goal is to have as many segments as possible for the measurement space. If you have 6" of measurable space, you can cut a 710ES or 710SS down to 6". However, this will give you 4 segments on the 710ES and only 3 on the 710SS. An uncut 710JS would allow for 6 segments in this space. Since there are more segments available, your resolution will be better.
Installation Tip: When the length of space to be measured falls in the middle of a segment, cut the sender to the shorter length. This will increase your gap or space at the top or bottom of the tank. However, for fresh tanks, we recommend leaving the larger gap at the top of the tank. The most important measurement on a fresh tank is when it is nearing empty. The opposite is try for grey, galley or black tanks. You want to leave the larger gap at the bottom of these tanks.
The 710ES is Recommended for Measurable Spaces Between 8 to 14 Inches Tall
The 710JS is Recommended for Measurable Spaces 4.5 to 8 Inches Tall
3 Options for Tanks Taller than 14 Inches
When faced with tanks taller than 14 inches, you have three possible solutions to measure the height of larger tanks.
Option #1: Stack two 710ES's for Measurable Spaces 17 to 26 Inches
This option requires an additional 710ES to be purchased. When faced with tanks of this height, installing stacked 710ES's is the best solution. As noted in the installation guide found in the owners manual, we recommend cutting each sender to equal lengths when possible. Only 710ES's can be stacked together.
Option #2: Use a Single 710SS for Measurable Spaces 14 to 18 Inches
This option may not allow for the maximum amount of segments for this length, but it is a cheaper alternative to purchasing an additional 710ES for stacking. An additional charge is applied when upgrading from a 710ES to a 710SS.
Option #3: Stack two 710SS's for Measurable Spaces 26 to 34 Inches
As with the 710ES, we recommend cutting each 710SS to equal lengths when possible. Only 710SS's can be stacked together.
When it comes to making these decisions, we always encourage a phone call or email. We are more than happy to walk you thru the process of purchasing and installing your SeeLeveL RV Tank monitor. We would love to share our knowledge and experience with you. Contact us 1-877-668-7813 or email firstname.lastname@example.org